
Qass. 
Book. 



\/Mn 



LESSONS AND PRACTICAL NOTES 



out 



STEAM 



THE STEAM EIGIIE, PROPELLERS, 

ETC., ETC., 



FOR 



oun§ (Engineers, Jitafetfs, mb diners* 



BY XHE. LATE 



¥. H. KING, U. S. & 



REVISED B¥ 



CHIEF ENGINEER £ W. KING, I. S. tt 









[fottrth EDITION, ENLARGED.], 




NEW YORK 
D. VAN NOSTRAND, 192 BROADWAY 

LONDON : 

TRttBNER & COMPANY. 

1863. 









5\ 



Entered, according to Act of Congress, in the year 1860, 

BY J. W. KING, 

In the Clerk's Office of the District Court of the United States for the Southern District of 

New York. 



JOHN T. TROW, 

PEWTBB, PTKREOTYPER, AND KLECTHOTTPXB, 

50 Greene Street, New York. 



INSCRIBED TO 

HON. GUSTAVUS V. FOX, 

ASSISTANT SECRETARY OP THE NAVY, 
TOKEN OF THE AID HE HAS EXTENDED TO THE ADVANCEMENT OF 
NAVAL IRON STEAMSHIP CONSTRUCTION. 






t 



- 



\ 



}> 






;> 



CONTENTS. 



Introduction, Page 5. 
CHAPTER I. 



Steam, 7. Mechanical Effect, 9. Expansion of Steam, 12. Table of Hyperbolic 
Logarithms, 14. Back Pressure, 16. Gain by Expanded Steam, 18. 

EXPANSION VALVES. 

Sickel's, 19. Stevens', 22. Allen & Wells', 23. 

SLIDE CUT-OFFS. 

Explanation, 24. Gridiron Valve, 26. Wabash Valve, 29, 

OTHER KINDS OF VALVES. 

Double Poppet, 30. Single Poppet, 81. Hornblower's, 32. Box Valve, 33- 
Equilibrium Slide, 34. Double Slide Valve, 34. Piston Valve, 35. Long 
D Slide, 36. Short D Slide, 37. Worthington Pump Valve, 38. Pitts- 
burg Cam, 39. 

CHAPTER n. 

THE INDICATOR AND INDICATOR DIAGRAMS. 

The Indicator, 41. Cylinder Diagrams, 44. Air-pump Diagrams, 66. Power 
Required to Work the Air-pump, 60. 

CHAPTER HI. 

THE HYDROMETER. 

The Hydrometer, 62. Loss by Blowing-off, 64. Gain by the Use of Heaters, 
4)8. Injection Water, 71. Evaporation, 72. Steam and Vacuum Gauges, 75. 



4 CONTENTS. 

CHAPTER IY. 

CAITSALTIES, ETC. 

Broken Eccentric, 79. Leaking "Vessel, 79. Irregular Feed, 80. Foaming, 81. 
Hot Condenser, 83. Getting Under Way, 85. Coming into Port, 86. 
Scaling Boilers, 88. On Coming to Anchor, etc., 89. Management of 
Fires, 90. Patching Boilers, 93, Sweeping Flues, 95. Ash Pits, 95. 
Smoke-pipe Stays, 96. Grate Bars, &c, 96. Broken Air-pump, 97. Bro- 
ken Cylinder-head, 98. Selection of Coal, 98. Safety Valve, 99. 

CHAPTER V. , 

MISCELLANEOUS. 

Theory of the Paddle Wheel, 101. Centre of Pressure, 114. Screw Propeller, 
116. Altering the Pitch, 132. Parallel Motion, 133. Strength of Mate- 
rials, 136. Surface - Condensers, 141. Cylindrical Boilers, 145. Boiler 
Explosions, 148. Horse Power, 150. Vibration of Beams, 152. Marine 
Economy, 154. Limit to Expansion, 155. The Proper Lift for a Valve, 
155. Temperature of Condenser, 156. 

CHAPTER VI. 

WESTERN RIVER BOAT ENGINE. 

Western River High-Pressure Engine, 159. Side Elevation, 159. End View, 
160. Explanations of Diagrams, 160. Hartuper's Lifter, 165. Stern Wheel 
Boats, 167. Dimensions and Proportions of the Magnolia, 169. 

CHAPTER VH. 

BOILERS, ETC. 

Water-Tube Boiler, 172. Horizontal Fire Tube, 173. Extracts from Report of 
Experiments made to Determine the Relative Efficiency of the Two Boilers, 
174. Western River Boilers, 179. Boiler Flues, 184. Riveting, 186. Su- 
perheated Steam, 189. Draft, 191. 

APPENDIX. 

MATERIALS. 

How to Test Iron, 194. Cast Iron, 195. Malleable Iron, 198. Steel, 202. Te- 
nacity of Metals, 206. Transverse Strength, 206. Resistance to Torsion, 
207. Results of Repeated Heating Bar Iron, 207. Strength of Joints of 
Boiler Plates, 209. 

THE ELEMENTS OP MACHINERY. 

Motion, 211. Application of Power, 212. The Lever, 215. Inclined Plane, 217. 
Wheel and Axle, 219. Pulley, 219. Screw, 223. Wedge, 224. Centre 
of Gravity, 225. Centre of Pressure, 225. Gravity, 225. Displacement of 
Fluids, 227. Table of Pressure, Temperature, and Volume of Steam, 228. 



INTKODUCTION. 



Writing a book and then apologizing for having 
written it, is hardly in accordance with our convic- 
tions ; "but considering, nevertheless, the eminent tal- 
ent which has preceded us upon the subject we have 
taken up, a few remarks of explanation may not be 
out of place. Books heretofore appearing on the 
steam engine, have been of two classes, or the work 
itself has been divided into two parts — the one for the 
theorist, the other for the practical man. In the one 
case long mathematical formulas have been produced, 
and in the other nothing but simple rules. The prac- 
tical man, therefore, who has not had the advantage 
of a mathematical education, has nothing presented to 
him but the bare rules, which he is compelled wholly 
to reject, or take entirely upon trust. Besides, these 
works extend over numerous volumes, the study of 
which involve much time, labor, and expense, and 
which usually disheartens the practical man before he 
has made much progress. Having had many of these 
difficulties to surmount in our earlier studies of the 
steam engine, we were led to the course of keeping a 
Steam Journal, in which we noted, from time to time, 
as we progressed, whatever we thought important, and 
was made clear to our mind ; and this course we would 
also recommend the young student ; for, however well 



6 IOTKODUCTION. 

it may be to study books containing other mens 1 
thoughts, when we write we are led to the habit of 
thinking for ourselves, which is of the highest impor- 
tance ; and, by keeping a journal, we have also the 
very great advantage of having always at our com- 
mand, in a condensed form, those things which are the 
more important, and which can be referred to at any 
time. 

Much of the present work has been taken from the 
Authors Journal, and the remainder has been sup- 
plied, from time to time, as he found leisure from his 
hours of business. 

Our object has not been so much to supply want- 
ing information, as to direct the student into the habit 
of thinking and reasoning for himself on those subjects 
which may be presented for his consideration, and 
which, in order that he may become eminent in his 
profession, he must thoroughly understand. It is not 
sufficient to assert that Newton said this, or somebody 
else said that. The reasons why they said it, and the 
fundamental principles upon which they based their 
conclusions, are necessary to be understood, in order 
to have a clear understanding of the subject ; and if 
we have succeeded in making any thing more clear, 
or in rendering any service to that class of persons 
who are eagerly seeking for information, but who re- 
quire some assistance to direct them in the proper 
channel, our only object in launching this, our little 
bark, on the troubled sea of authorship, is fully accom- 
plished, conscious all the while, however, of the many 
imperfections it contains. 



LESSONS AND PRACTICAL NOTES, 



CHAPTEE I. 



STEAM. 



Steam is a thin, elastic, invisible fluid, generated 
by the application of heat to any liquid, usually water. 
That, however, which is generated while the water 
is in a state of ebullition, is alone generally termed 
steam, while that which is formed while the surface of 
the water is quiescent, is denominated vapor — a dis- 
tinction, to our mind, without much difference. 

The mean pressure of the atmosphere at the sur- 
face of the ocean is equal to 14.7 pounds per square 
inch, or is equivalent in pressure to a column of mer- 
cury 29.9212 inches in height. Under this pressure, 
fresh water boils at a temperature of 212° Fahrenheit. 

The 212° is, however, not the total number of de- 
grees in the steam, but simply that which is indicated 
by the thermometer, and which is termed sensible 
heat ; for we all know that to raise water from the 
freezing to the boiling point requires a certain time, 
and a certain amount of fuel; and we know farther, 
that when the water commences to boil, it does not all 
evaporate at once, but that the evaporation goes on 



8 STEAM. 

gradually, and the time, and hence the fuel required 
to evaporate it, is much greater than that required to 
raise it from the freezing to the boiling point. This 
extra heat must have gone off somewhere, and must 
be in the steam, but as it is not indicated by the ther- 
mometer, it is termed latent heat. When the steam is 
reconverted into water, the latent heat becomes again 
sensible, which is evidenced by the large amount of 
water required to condense a small amount in the 
shape of steam. The precise ratio the one bears to 
the other shows the latent, compared with the sensible 
heat. 

The subject of latent heat has been one of unusual 
interest, ever since the invention of the steam engine, 
and numerous theories have been advanced, and nu- 
merous experiments made — some of -them not very 
carefully — in order to determine the exact law it fol- 
lowed ; but none, up to Regnault's time, seem to have 
settled the subject satisfactorily. Some maintained 
that the latent heat of steam was a constant quantity, 
some that the sum of sensible and latent heat was a 
constant quantity, and that quantity was 1202° Fahr- 
enheit. This was the most popular theory, and was 
the one generally adopted by engineers. Others, 
again, maintained that neither the sensible, latent, nor 
sum of the sensible and latent heats, were a constant 
quantity, but that they all varied. The exact ratio, 
however, in which they varied was not established 
until Eegnault undertook his able series of experi- 
ments at the instigation of the French Government. 
These are the latest and most reliable experiments, 
and we subjoin, therefore, a table compiled from his 
labors, which we earnestly recommend to the attention 
of the reader. 



MECHANICAL EFFECT. 



REGNAULTS EXPERIMENTS. 



Degrees of heat contained in saturated steam, in Fahrenheit degrees 
of heat and English inches. 



iture of the 
ed steam. 
it the point 
ensation.) 


Corresponding elastic 
force 


Total heat, latent 

heat plus sensible 

heat above 

0° Fahrenheit. 


Temperature of the 
Saturated steam. 

(Vapor at the point 
of condensation.) 


Corresponding elastic 
force 


Total heat, latent 

heat plus sensible 

heat above 

0* Fahrenheit. 


Tempers 
Satural 

(Vapor i 
of cond 


In 

Inches. 


In Atmo- 
spheres. 


In 

Inches. 


In Atmo- 
spheres. 


°Pah. 
















32 


0.1811 


0.006 


1123.70 


248 


58.7116 


1.962 


1189.58 


50 


0.3606 


0.012 


1129.10 


266 


79.9321 


2.671 


1194.98 


68- 


0.6846 


0.023 


1134.68 


284 


106.9930 


3.576 


1200.56 


86 


1.2421 


0.042 


1140.16 


302 


140.9930 


4.712 


1205.96 


104 


2.1618 


0.072 


1145.66 


320 


183.1342 


6.120 


1211.54 


122 


3.6212 


0.121 


1151.06 


338 


234.7105 


7.844 


1216.94 


140 


5.8578 


0.196 


1156.64 


356 


297.1013 


9.929 


1222.52 


158 


9.1767 


0.306 


1162.04 


374 


371.7590 


12.425 


1227.92 


176 


13.9621 


0.466 


1167.62 


392 


460.1943 


15.380 


1233.50 


194 


20.6869 


0.691 


1173.02 


410 


560.9673 


18.848 


1238.90 


212 


29.9212 


1.000 


1178.60 


428 


684.6584 


22.882 


1244.48 


230 


42.3374 


1.415 


1184.00 


446 


823.8723 


27.535 


1249.88 



Fig. 1. 



W 



*0 



Kio. 2. 







MECHANICAL EFFECT. 

We will now take into consideration the mechani- 
cal effect of steam, and a common-place demonstration 
will serve our purpose. 

Suppose a cylinder, A, Fig. 
1, to be one square inch in 
area of cross section, and fitted 
with a steam tight piston, at- 
tached by means of a flexible 
cord to the weight #, which is 
of sufficient size to balance the 
weight of the piston, and all 
the parts to work without 
friction; Now suppose a quan- 
tity of water, equal to one 



cubic inch, to be placed in the bottom of this cylinder, 



10 MECHANICAL EFFECT. 

and a fire to "be lighted under it. The temperature 
of the water will gradually rise until it attains 212°, 
when it will commence to boil, and the piston will 
soon begin, and continue to rise — if the cylinder be 
long enough — until it obtains a height of 1700 inches 
from the base. This 1700 is the volume of steam at 
atmospheric pressure, the water being 1, from which it 
is generated. If, now, we suppose to be added to the 
weight, £, another weight equal to the pressure of the 
atmosphere — or a fraction less, so that motion may en- 
sue — and the steam under the piston to be condensed, 
the piston will return to the bottom of the cylinder 
by the pressure of the atmosphere, through a space 
of 1700 inches, and will have raised the extra weight of 
14.7 lbs. appended to 3, up that distance. Hence this 
cubic inch of water, by its evaporation, produced a 
mechanical effect of raising 14.7 pounds through a 
space of 1700 inches == (14.7 X 1700) = 24,990 pounds 
through one inch. 

Let us now take another cylinder, B, Fig. 2, similar 
in every respect to A, excepting that the piston has a 
weight laid upon it equal to the pressure of the atmo- 
sphere, viz., 14.7 pounds, and suppose a fire to be 
lighted under this cylinder. The water, as in the 
other case, will be heated up to the boiling point, — 
which, in this case, will be 250°, corresponding to the 
pressure of two atmospheres — when it will commence 
to evaporate, and the piston will rise until it obtains a 
height of 900 inches from the base, this being the 
volume of steam under the pressure of two atmo- 
spheres, water being 1. If, now, we suppose this pis- 
ton to be fixed where it is, the weight removed from 
the top of it and applied to c, then the steam condensed 
and the piston unfixed, it will return to the bottom of 



MECHANICAL EFFECT. 11 

the cylinder, raising the weight applied to c, up a dis- 
tance of 900 inches. Now, then, since the weight of 
14.7 lbs. was first raised 900 inches on the top of the 
piston, and afterwards raised the same distance by be- 
ing attached to c, the total distance moved = (900 X 2) 
= 1800 inches, which is equal to (14.7 X 1800) =a 26460 
pounds raised one inch. The difference, therefore, be- 
tween the work done in the first and second case 
= (26460— 24990) =1470 lbs. raised one inch high, 
which is 5.88 per cent, of the first number. If this 
extra work was obtained without any extra fuel, which 
would be the case were the total heat in steam at all 
temperatures a constant quantity, it would be all gain, 
but as such is not the case, and as more heat is required 
in the latter than in the former case, we will see what 
this amounts to, and the difference between this loss 
and the other gain will show the true gain. In the 
first instance, it will be seen that the total heat in the 
steam was 1178.6°, and in the second, 1190°; hence, 
supposing the water in both cases to be at a tempera- 
ture of 100° before the fires are lighted — which is 
about the temperature at which water is fed into ma- 
rine boilers — there would be required in the latter 
case (1190°— 100) == 1090° from the fuel, and in the 
former case (1178.6°— 100°) = 1078.6° from the fuel; 
difference 11.4°, which is 1.057 per cent, of 1078.6°. 

The extra fuel, therefore, required under the pres- 
sure of two atmospheres is 1.057 per cent., and the 
extra work done is 5.88 per cent., leaving a gain of 
4.823 per cent. 

In the same way we could ascertain what the gain 
would be at any other pressure, either higher or lower ; 
but these examples suffice to show that the higher the 
pressure of the steam, the greater is the mechanical 



12 EXPANSION OF STEAM. 

effect with the same amount of fuel, but the gain is 
small, and in practice, therefore, where great accuracy 
is not required, it is neglected altogether. 

Starting, therefore, from the assumption that the 
mechanical effect performed by the same amount of 
fuel is the same, no matter what the pressure may be 
under which the steam is generated, we shall proceed 
to the study of the 

EXPANSION OF STEAM. 

Opening a communication with the cylinder and 
shutting it off again before the piston arrives at the 
end of the stroke is called expansion of steam, or work- 
ing steam expansively. Thus, supposing steam to be 
admitted into the cylinder until the piston arrives at 
half stroke, and the communication then to be shut off, 
the steam already in the cylinder, by its expansion, 
will force the piston to the end of the stroke ; by 
which arrangement we gain all the work performed 
after the steam is cut-off. 

fig. 3. Take, for instance, a cylinder, A, Fig. 3, 

two units in length, one unit in area of 
cross section, and an initial pressure of 1, 
the work performed during the first half 
stroke, i. &, while the piston travels from 
b to e, will be 1 X 1 X 1 (area x pressure 
X distance travelled ==) 1, and the work 
9 performed during the latter half stroke = 
1 X .69 X 1 = .69, the total work, there- 
_ fore, performed throughout the stroke 
1,b9 = 1.69. Now, if the steam, instead of be- 
ing expanded from c to <#, had been exhausted at <?, the 
total work performed would have been only 1 instead 



EXPANSION OF STEAM. 13 

of 1.69, and the quantity of steam would have been the 
same, hence we see that by cutting off at one half the 
same steam performs 69 per cent, more work. This 69 
per cent, is what is termed the gain in cutting off, but it 
does not, however, represent the saving in fuel, as we 
will show presently; but before proceeding to illus- 
trate that subject we will explain to the student, from 
what source we derive this 69. 

Marriotte's law of gases is, that the spaces occupied 
are inversely as the pressures. That is to say, if steam 
of 20 pounds pressure per square inch, be allowed to 
expand into double the space, the pressure will be 
10 lbs. ; if triple, 6-| lbs. ; if four times, 5 lbs. ; if five 
times, 4 lbs., and so on. This theory would be liter- 
ally correct did the temperatures remain constant ; but 
as the temperature of all gases becomes reduced by ex- 
pansion, the law does not hold good ; nevertheless, in 
the steam engine, where there are so many extraneous 
circumstances which practically affect all calculations 
appertaining to the same, it is considered all that is 
ever required, and from its extreme simplicity is uni- 
versally adopted. 

From this law the pressure can be 
ascertained approximately by dividing 
the cylinder into a number of equal x 

parts, say eight, ascertaining the pres- x 

sure at each of those points, and taking t 
the mean. If the initial pressure, as 8000 
before, be supposed to be unity, the 6666 
pressure at each of the first four divi- 5714 
sions cutting off at half stroke will be 
1; at the fifth division (f =) .8 ; at the *& 
6th (|) = .6666; at the 7th (-f =) .5714; 
at the 8 th (| =) .5 ; the mean pressure, therefore, by 



.500 
.53S0 
^6345 



14 



TABLE OF HYPEEBOLIC LOGARITHMS. 



this process, after the steam is cut off = .6345, and the 
mean pressure before it is cut off = 1, the mean, there- 
fore, throughout the stroke = ( '— 



)= 



.8172.- 



This, however, is only an approximation, and in order 
to arrive at any degree of accuracy, the divisions would 
have to be very numerous, which would render the 
operation tedious and lengthy. Fortunately, however, 
we can dispense with this part of the calculation alto- 
gether, for the Naperian or Hyperbolic logarithms, as 
set forth in the following table, furnish to our hand 
the ratios of pressures : 



TABLE OF HYPERBOLIC LOGARITHMS. 





o 




y 




o 




o 




o 


u 




u 








u 




u 






o . 
^ bo 


M 




rfi 


& £ 


© 


£ to 


o 


*3 ._• 


a 




'- o 

|3 


a 




2 

3 


T, O 


a 

3 


u O 
Pi 


a 

3 


U O 
©J 


fc 


£ 


fc 


>> 

w 


fc 


w 


fc 


>> 


fc 


& 


1.05 


.049 


3.05 


1.115 

us! 


5.05 


1.619 


7.05 


1.953 


9.05 


2.203 


1.1 


.095 


3.1 


5.1 


1.629 


7.1 


1.960 


9.1 


2.208 


1.15 


.140 


3.15 


1.147 


5.15 


1.639 


7.15 


1.967 


9.15 


2.214 


1.2 


.182 


3.2 


1.163 


5.2 


1.649 


7.2 


1.974 


9.2 


2.219 


1.25 


.223 


3.25 


1.179 


5.25 


1.658 


7.25 


1.981 


9.25 


2.225 


1.3 


.262 


3.3 


1.194 


5.3 


1.668 


7.3 


1.988 


9.3 


2.230 


1.35 


.300 


3.35 


1.209 


5.35 


1.677 


7.35 


1.995 


9.35 


2.235 


1.4 


.336 


3.4 


1.224 


5.4 


1.686 


7.4 


2.001 


9.4 


2.241 


1.45 


.372 


3.45 


1.238 


5.45 


1.696 


.7.45 


2.008 


9.45 


2.246 


1.5 


.405 


3.5 


1.253 


5.5 


1.706 


7.5 


2.015 


9.5 


2.251 


1.55 


.438 


3.55 


1.267 


5.55 


1.714 


7.55 


2.022 


9.55 


2.257 


1.6 


.470 


3.6 


1.281 


5.6 


1.723 


7.6 


2.028 


9.6 


2.262 


1.65 


.500 


3.65 


1.295 


5.65 


1.732 


7.65 


2.035 


9.65 


2.267 


1.7 


.531 


3.7 


1.308 


5.7 


1.740 


7.7 


2.041 


9.7 


2.272 


1.75 


.560 


3.75 


1.322 


5.75 


1.749 


7.75 


2.048 


9.75 


2.277 


1.8 


.588 


3.8 


1.335 


5.8 


1.758 


•7.8 


2.054 


9.8 


2.282 


1.85 


.615 


3.85 


1.348 


5.85 


1.766 


7.85 


2.061 


9.85 


2.287 


1.9 


.642 


3.9 


1.361 


5.9 


1.775 


7.9 


2.067 


9.9 


2.293 


1.95 


.668 


3.95 


1.374 


5.95 


1.783 


7.95 


2.073 


9.95 


2298 


2. 


.693 


4. 


1.386 


6. 


1-792 


8. 


2.079 


10, 


2.303 


2.05 


.718 


4.05 


1.399 


6.05 


1.800 


8.05 


2.086 


15. 


2.708 


2.1 


.742 


4.1 


1.411 


6.1 


1.808 


8.1 


2.092 


20. 


2.996 


2.15 


.765 


4.15 


1.423 


6.15 


1.816 


8.15 


2.098 


25. 


3.219 


2.2 


.788 


4.2 


1.435 


6.2 


1.824 


8.2 


2.104 


30. 


3.401 


2.25 


.811 


4.25 


1.447 


6.25 


1.833 


8.25 


2.110 


35. 


3.555 


2.3 


.833 


4.3 


1.459 


6.3 


1.841 


8.3 


2.116 


40. 


3.689 


2.35 


.854 


4.35 


1.470 


6.35 


1.848 


8.35 


2122 


45. 


3.807 


2.4 


.875 


4.4 


1.4S2 


6.4 


1.856 


8.4 


2.128 


50. 


3.912 


2.45 


.898 


4.45 


1.493 


6.45 


1.864 


8.45 


2.134 


55. 


4.007 


2.5 


.916 


4.5 


1.504 


6.5 


1.872 


8.5 


2.140 


60. 


4.094 


255 


.936 


4.55 


1.515 


6.55 


1.879 


8.55 


2.146 


65. 


4.174 


2.6 


.956 


4.6 


1.526 


6.6 


1.887 


8.6 


2.152 


70.. 


4.248 


2.65 


.975 


4.65 


1.537 


6.65 


1.895 


8.65 


2.158 


75. 


4.317 


2.7 


.993 


4.7 


1.548 


6.7 


1.902 


8.7 


2.163 


80. 


4.382 


2.75 


1.012 


4.75 


1.558 


6.75 


1.910 


8.75 


2.169 


85. 


4.443 


2.8 


1.032 


4.8 


1.569 


6.8 


1.917 


8.8 


2.175 


90. 


4.500 


2.85 


1.047 


4.85 


1.579 


6.85 


1.924 


8.85 


2.180 


95. 


4.554 


2.9 


1.065 


4.9 


1.589 


6.9 


1.931 


8.9 


2.186 


100. 


4.605 


2.95 


1.082 


4.95 


1.599 


6.95 


1.939 


8.95 


2.192 


1000. 


6.908 


3. 


1.099 


5. 


1.609 


7. 


1.946 


9. 


2.197 


10000. 


9.210 



C c 



EXPANSION OF STEAM. 15 

The hyperbolic logarithm of any number can be 
found by multiplying the common logarithm by 
2,30258509. 

From the nature of hyperbolic logarithms they are 
thus very useful in working steam expansively. 

Let the Line A, B, Fig. 5, represent FlG - 5 - 
the pressure of steam — which we will as- 
sume to be unity — at the time the cut-off 
valve closes ; C, D, half the length of A, 
B, and the line A, C, a hyperbolic curve, 
.69+ from the table gives the mean leugth 
of all the ordinates, 1, 2, 3, 4, &c, which 
before we had to arrive at by approxima- 
tion. If the cut-off valve, instead of closing 
at half stroke, had closed at some other 
point, say, when the piston had traveled 
only one-fourth its distance, C, D, would be one-fourth 
of a, b, and the curve A, C, would have extended from 
a to <?, giving 1.38 -f- as a mean of all the ordinates 
below a, 5. 

All we require then in working examples in ex- 
pansion of steam, according to Marriotte's law, is to 
know the initial pressure and point of cutting off, from 
which we can deduce the mean pressure, pressure at 
the end of the stroke, percentage of gain, &c, by 
having before us a table of hyperbolic logarithms; 
but if it be required to make such calculations, when a 
table of this kind is not come-at-able, it can be done in 
the manner we have previously shown. 

Example 1st. Suppose you have a cylinder in 
which you are using steam of 20 pounds pressure per 
square inch, inclusive of the atmosphere, and cut off at 
half stroke, what is the mean pressure, pressure at the 
end of the stroke, and per centage of gain. 



16 BACK PRESSURE. 

Ans. 1st. From the foregoing considerations we 
know that had the pressure of steam been 1 pound in- 
stead of 20, all we would have to do would be to take 
.69314 out of the table, add 1 to it and divide by 2; 
therefore to find the mean pressure we have this rule : 
As the number of times the steam is expanded, is to the 
hyperbolic logarithm of that number plus 1, so is the 
initial to the mean pressure, hence 2 : 1.69314 : : 20 : 
16.9314lbs. mean pressure. 

Ans. 2d. 20-f-2=10 lbs. pressure at the end of the 
stroke. 

Ans. 3d. "Work performed before expansion, 1. 
after expansion, .69314. Therefore 1 : .69314: : 100 : 
69.314 per cent, gain by cutting off at half stroke. 

Back Pressure. 

Inasmuch as it is impossible in practice to obtain 
a perfect vacuum, there is always a certain amount of 
steam in the cylinder opposed to the motion of the 
piston, and this is termed bach pressure. Suppose for 
example, there was in the above instance 4 lbs. per 
square inch back pressure, the mean effective, or un- 
balanced pressure, would be 16.9314—4—12.9314 lbs., 
and the unbalanced pressure at the end of the stroke 
would be 10— 4=6 lbs. 

Example 2d. Suppose the steam in example 1st 
had been cut off at a \ from commencement of stroke, 
what would have been the mean pressure, pressure at 
the end, and percentage of gain in that case ? Also 
the mean unbalanced pressure, and unbalanced pressure 
at the end, the back pressure being 4 lbs per square 
inch? 



BACK PRESSURE. 17 

Arts. 1st. 4 : 2.38629 : : 20 : 11.93145 lbs. mean pres- 
sure. 

Ans. 2d. 20 -f- 4 = 5 lbs. pressure at the end. 

Ans. 3d. 1 : 1.38629 :: 100: 138.629 per cent. 

Ans. 4th. 11.93145—4=7.93145 mean unbalanced 
pressure. 

Ans. 5th 5— 4 = 1 lb. unbalanced pressure at the 
-end. 

It is useless hereto multiply examples ; those already 
given we consider sufficient to give the student a clear 
understanding of the manner in which these calcula- 
tions are made, but we would recommend him to make 
a number of others for himself, and work them out so 
as to render himself the more familiar and ready with 
the modus operandi. 

We come now to the percentage of gain of fuel by 
using steam expansively. It has been previously 
shown that when the steam is cut off at one half, the 
work done before expansion takes place being repre- 
sented by 1, the work done afterwards is .69 ; the total 
work therefore performed is 1.69; now had not the 
cut-off valve closed at all, the total work performed 
would have been 2. Hence by this operation we have 
the power of the engine reduced from 2 to 1.69. It is 
therefore necessary to increase the initial pressure of 
steam to make up this decreased power ; and keeping 
in view Marriotte's law, we will let this pressure be 
represented by x ; hence 2 : 1.69 : : x : .845 a?, the mean 
pressure. It is manifest that the mean pressure in this 
case must be the same as if the steam followed full 
atroke, in order that the powers may be the same; 
consequently 

.845 x = 1 lb. 

x = 1.18 lb. initial pressure. 



18 GALtf BY EXPANDED STEAM. 

But only half a cylinder full of this steam is used to 
every fall cylinder of the other, consequently the dif- 
ference between 1.18-^2 and 1, equals the saving, 
which is 41 per cent. 

To ascertain the saving of steam at any other point 
of cutting off, take the hyperbolic log. of 3, 4, 5, 6, 
&c. as the cutting-off point may be i, J, i i &c, and 
proceed in the same manner, or, in other words, divide, 
the whole length of the stroke by the portion traveled 
before the steam is cut off; take the hyperbolic log. of 
the quotient and proceed as above.. 

The 41 per cent, in the above example, is the 
saving in steam — that is to say, should a steamer, 
using steam full stroke, perform a certain distance 
in a certain time, cut the steam off at half-stroke, 
and increase the initial pressure in the ratio of 1 
to 1.18, she would perform the same distance in the 
same time with 41 per cent, less steam. Not 41 per 
cent., less coals put into the furnaces, but 41 per cent, 
of that which reaches the cylinders minus the loss 
from condensation due to expansion, i. e. that por- 
tion of the fuel not combustible, and that portion pass- 
ing out of the chimney in the shape of heat to produce 
draft, together with the loss from radiation and con- 
densation before the steam reachers the cylinders must 
first be deducted. When this is done it will be found 
that the actual saving will be reduced to less than 20 
per cent., which is about the real saving of fuel in 
practice cutting off at half stroke, and pro- rata for any 
other point — varying somewhat according to better or 
worse constructions. Any engineer can satisfy himself 
on this point by using his steam with and without ex- 
pansion for a sufficient given time, carefully weighing 
all the coals and recording all the data. 



EXPANSION VALVES. 



19 



This should not therefore be confounded with the 
69 per cent., which is theoretically the increased work 
performed by the same steam over what it would have 
performed had it not been cut off at all. 



Fig. i. 



Expansion Valves. 

There are a variety of expansion valves and arrange- 
ments for cutting off steam ; the principles operating 
the more important of which we will now proceed to 
examine. The following diagrams or sketches will 
serve our purpose. We shall simply explain the lead- 
ing features of each, in order to give an understanding 
of the principles that govern them, leaving the student 
to suggest for himself the 
alterations in the mechani- 
cal arrangement to adapt 
them to different types 
and arrangements of en- 
gines. 

i Figure 1 is a diagram 
of Sickel's momentarily 
adj ustable cut-off, in which 
A, A, is the steam valve 
of the double poppet con- 
struction ; B, B, valve 
stem; C, dash-pot, filled 
with water up to the line 
1, 2 ; D, plunger, fitting 
in the dash-pot ; E, stuf- 
fing-box, which is packed 
air and water-tight; «?, 
hole in the bottom of the 
plunger D, to allow the 
water to enter when the plunger strikes it; 5, a 




20 EXPANSION VALVES. 

rod communicating motion to the wiper F, which 
trips the valve ; A, a rod receiving motion from the 
air-pump beam or any other part having motion coin- 
cident with that of the piston. The motion of A is 
communicated through the vertical rod, having c as a 
fixed centre to 5, and thence to the wiper F. The 
manner in which this cut-off operates is this: The 
valve stem, instead of being permanently attached to 
the lifting rod, is secured to it by a clutch and spring. 
The valve is lifted by the eccentric, (operating as in 
other cases,) but before it reaches its seat again, the 
wiper F, which vibrates back and forth, strikes the 
clutch, and detaches the valve from the lifter; the 
valve then, from the action of gravity, would fall, and 
strike its seat with a heavy blow; to prevent which, 
and allow the valve at the same time to fall quickly, 
it is attached to the plunger D, working in the dash- 
pot C. By this arrangement, before the valve reaches 
its seat, the plunger D strikes upon the water in the 
lower part of the dash-pot C, which is called the secon- 
dary reservoir, and thereby allows the valve to close 
without slamming, the water escaping into the cavity x } 
and also around the plunger, into the upper or primary 
reservoir. The plunger D, being hollow, small holes 
are bored into it in the vicinity of the line 1, 2, to 
allow the water to escape into it also. 

We see that the cutting-off is effected by the wiper 
F tripping the valve ; the sooner therefore the valve 
is tripped, the sooner the steam will be cut off. Now 
the manner in which this is made an adjustable cut-off, 
is accomplished by moving the handle f backward or 
forward on the arc <7, which will move the centre c to 
one side or the other of its present position, the center e- 
remaining constantly fixed, and therefore giving the 



EXPANSION VALVES. 21 

wiper F a greater or less distance to travel before 
striking the clutch. By this means the cut ting-off 
point can be varied for any part of the stroke. The 
handle/ can be put in such a position that the valve 
will not be tripped at all, or it can be placed so that 
the valve will not lift at all, being exactly in the ver- 
tical position when the lifter commences to rise. The 
engine can be thus stopped by this cut-off. For the 
other end of the cylinder there is another dash-pot, 
<fcc., similar to the one described, the wiper being ope- 
rated by a rod similar to #, attached to the center d. 

Should there be too much water in the dash-pot, 
the valve will not seat quickly, but " hang," as it is 
technically termed. At a there is a cock for the pur- 
pose of supplying it with water. Attached to the 
dash-pot, there is usually another cock or valve for 
the purpose of letting out any superfluous water. In- 
sufficient water is evidenced by the slamming of the 
valve. 

This cut-off was formerly made without the wiper 
F, there being used instead a sliding cam, shaped 
something like this <|. As the valve rose up, the 
clutch struck the bevel on this cam, which forced the 
clutch out of its position, and allowed the valve to fall. 
With this arrangement, however, it will be seen that 
the valve must trip while it is rising, and as it is at its 
highest position when the piston is about half stroke, it 
cannot be possible to cut off by this mode longer than 
half stroke ; but with the arrangement of the wiper, it 
will be seen, inasmuch as it vibrates back and forth, 
that the valve can be just as well tripped on its descent 
as when rising, and this is the reason why it was sub- 
stituted for the cam. 

" Stevens? — The next cut-off that we shall take 



22 



EXPANSION VALVES. 



Fig. 2. 



^ 



into consideration is Stevens's, a diagram of which is 
shown in figure 2. A A are the steam toes ; B B, 
the steam-lifting toes ; D, rock-shaft arms ; C C, the 
valves ; #, pin in rock-shaft 
arm for eccentric hook. The 
manner in which this is 
made an adjustable cut-off, 
is by raising or lowering the 
toes A A, thereby giving 
them more or less lost mo- 
tion. In the position in 
which they are shown in the 
diagram, it will be seen that 
they will have to travel a 
considerable distance before 
touching the toes B, B, and 
as the piston is in motion 
during this time; and the 
steam valve closed, the 
steam will be acting expan- 
sively. If the end of the toes A A be dropped lower 
down, the steam will be cut off shorter ; if raised higher 
up, longer. By dropping the toes down, however, we 
diminish the lift of the valve, and also alter the lead. 
To retain the one, we raise the pin a in the rock-shaft 
arm, and the other we turn the eccentric a little ahead. 
To alter the point of cut-off, therefore, while the engine 
is in motion, so as to cut off shorter, we have first to 
drop the toes A A, then raise the pin a, and set the ec- 
centric ahead. To cut off longer, reverse the operation. 
The number of things required to be altered in 
changing the point of cutting-off is a very great objec- 
tion to this arrangement. In practice it has seldom 
been accomplished without stopping the engine. 




EXPANSION VALVES. 



23 



Allen and Wells. — This cut-off is represented by- 
sketch, figure 3. A, A, are the exhaust toes ; B B, 
steam toes; C C lifting toes ; D D, the valves ; E E', 



Fig. 3. 



3 




palls fitted to the end of the toes B, B' ; F, rock-shaft 
arm, which is operated from the eccentric in the usual 



24 SLIDE CUT-OFFS. 

way ; G G, a cross arm secured to the end of the rock- 
shaft arm ; a a, rollers on the end of the cross-arm G, 
G' ; H H, two arms fitted loosely on the rock-shaft. 
These arms receive their motion from any part of the 
engine having motion nearly coincident with that of 
the piston ; b b', rollers on these arms. This cut-off 
operates thus : The rock-shaft is put in motion by the 
eccentric. The pall E resting upon the roller a, is 
raised, and with it the toe B, and lifter toe C ; but 
after the pall E is raised up so as to clear the roller &, 
the pall E slides in on top of b, which, having a down- 
ward motion, lowers the valve, while the rock-shaft 
arm continues to rise. The rollers b b', being attached 
to the arms H H, which having motion nearly coinci- 
dent with that of the piston, start to go down at nearly 
the same time the rock-shaft arm starts to rise. Now 
then by turning around the right and left-hand screw 
c c, the rollers b b\ will be set further apart, or closer 
together, and will therefore alter the time they will 
clear the end of the pall E, and hence the point of cut- 
ting off. To follow farther separate the rollers b b\ 
to cut off shorter, screw them closer together. In 
altering the point of cutting off we have nothing to do 
but to turn around the screw c c. 

This cut-off is like " Sickel's " momentarily adjust- 
able, but it cannot, however, be made to cut off quite 
so short as " Sickel's." 



SLIDE CUT-OFFS. 

In the use of the ordinary three-ported slide-valve, 
or other slide-valves combining both the steam and 
exhaust, the expansive principle can be carried only 
to a very small extent, owing to the derangement of 



SLIDE CUT-OFFS. 



25 



the exhaust passages. Suppose, for instance, that suffi- 
cient lap be given to the steam side of the valve to 
cause the steam to be shut off at half-stroke, and sup- 
pose the same amount of lap be given also to the ex- 
haust side, it is manifest, that when the steam is shut 
off, the exhaust will be shut off also, and the pent up 
steam, therefore, having no escape, and increasing in 
pressure as the piston approaches the end of the stroke, 
will act as a serious retarding force. This arrange- 
ment, therefore, cannot operate. 

Now, then, suppose that we put lap on the steam 
side, as before, but none on the exhaust, in which 
event another difficulty equally great presents itself. 
It is this : 

Supposing the valve, Fig. 4, to have neither lap 
nor lead, when the end a arrives at a\ steam will just 
begin to be admitted into the cylinder, but the point 



Fig. 4. 




5, at the same time, will have arrived at the point £', 
and steam just begin also to exhaust ; now, then, let 
half an inch be added to each end of the valve at a 
and 5, when the valve begins to open to steam in this 
case, a, instead of being at a\ will be half an inch past 
it ; and, as there has been no lap added to the exhaust 
side, b will be half an inch past b f , so that the exhaust 



26 



SLIDE CUT-OFFS. 



must have opened considerably before the piston ar- 
rived at the end of the stroke ; hence, in this case, we 
exhaust too soon. 

All we can do, therefore, in practice, is to strike a 
mean between these evils ; that is to say, when we add 
lap to the steam side, add lap also to the exhaust side, 
but not so much so that we open the exhaust before 
the piston arrives at the end, and close it again before 
it reaches the other end. The shortest this kind of 
valve can be made to cut-off to advantage in practice, 
is considered about J- from commencement of stroke ; 
but even this we consider most too short for beneficial 
working of large engines. 

Owing to these confined limits, the beneficial re- 
sults obtainable from the expansive principle by this 
arrangement is very small, which has led to the adop- 
tion of an independent slide cut-off valve, situated on a 
separate face, back of the steam valve, as shown in 



Fig. 5. 




Fig. 5, in which a' is the steam, and b b the cut-off 
valve. The valve a having only sufficient lap to cover 
the ports a' a' fairly, when it is in the middle of 
the stroke, operates as in other cases, but the lap 
on bb can be made to any required extent, so that 



SLIDE CUT-OFFS. 27 

during a large part of the stroke the ports V V 
are closed, preventing further access of steam to the 
cylinder, notwithstanding the steam valve itself is 
open. The valve b b is operated by an independent 
eccentric, through the valve stem E. In the position 
shown in the figure the steam is cut off about half 
stroke : d' shows another opening covered with the 
valve d, having a stem c sliding loosely through the 
valve bb ; the other end of the stem passing through 
the chest, has a handle attached to it for the purpose 
of moving the valve d, in order to open the port d\ 
when the engine is stopped. This is necessary, for the 
reason that the engine may stop when the valve b b is 
in such a position as to prevent the steam from enter- 
ing to the steam valve «, and the engine could not, 
therefore, be started. In the figure, the cut-off valve 
has but two ports for* the admission of steam, but any 
number of ports can be made — the more numerous, 
the less stroke will be required to get the necessary 
opening. This is what is termed the gridiron valve, 
from the resemblance it bears to that very useful in- 
strument. 

After this valve is once made, the point of cutting 
off usually remains fixed, but it can, however, be varied 




within narrow limits by altering the stroke of the 
valve. Thus, in Fig. 6, supposing the end of the valve 
stem to be raised from a to 5, the valve, instead of 



28 SLIDE CUT-OFFS. 

being closed, as shown, will be open the distance b <?, 
and will therefore have that much additional to travel 
before the steam is cut off; hence, by increasing the 
travel of the valve we increase the point of cutting off, 
and conversely, supposing the pin a had been lowered 
in the rock-shaft arm the distance a e 1 equal to a 5, 
the ports, instead of being closed, as shown, would 
be closed the distance be; the steam, therefore, would 
be cut off sooner. But by altering the point of cutting 
off we also alter the lead of the valve ; for, taking the 
case in which we increased the travel of the valve, we 
see that when it would have been closed with the 
original lead, it lacked the distance b c. If its travel 
had been reduced, it would have lacked that much of 
being open. To obviate this, whenever the travel of 
the valve is altered, the eccentric should also be altered, 
so as to retain the original lead.* 

If the travel of the valve be made too great, the 
valve d will pass entirely over the port d\ and gradu- 
ally close <?', unless they be set some distance apart. 
If the travel be made too small, the steam will be shut 
off, and the motion of the eccentric being reversed 
long before the piston arrives at the end of the stroke, 
steam will be admitted to it again before the steam 
valve* closes. 

From the above facts, and the figure before us, we 
draw the following general conclusions in reference to 
this kind of slide cut-off valves : 

That, with a given amount of lap, the cutting off 
point can be varied from the longest point of cutting 
off allowable by said lap, to a certain point within the 
stroke, by reducing the stroke of the valve and alter- 
ing the eccentric so as to retain the original lead. If 
the stroke be reduced beyond this, steam will be shut 



SLIDE CUT-OFFS. 



29 



off and given to the piston again before it arrives at 
the end of the stroke. In practice, this variation will 
not amount to more than from about £ to f of the 
stroke. 

In altering the stroke of the valve, the slot through 
which the pin a moves should be an arc of a circle, 
struck with a radius equal to the length of the link d a, 
and with d as a centre. 

With equal leads, the cutting off point cannot be 
effected equally on both ends of the cylinder with a 
slide valve, owing to the connecting rod acting out of 
parallelism, or, in other words, owing to the crank not 
being at 90° when the piston is half way. The shorter 
the connecting rod, the greater the discrepancy. 



Fig. 6*. 



CONNECTS TO CONDENSER 




\ wmM m I JJF»P1 ' I I myfhmm 




Fig. 6J, is an arrangement of cut-off valve as con- 
structed by Messrs. Merrick & Son, of Philadelphia, 
in 1855, for the U. S. Steam Frigate " Wabash." 

In consequence of the satisfactory manner in which 
it worked on board that vessel ; its simplicity, and 
easy adjustment for cutting off at any portion of the 



30 OTHER KIND OF VALVES. 

stroke likely to be required, it has been applied to 
nearly all the U. S. Screw ships recently constructed, 
as also to a number of other engines. C is the steam 
valve ; T> D are the cut-off valves, attached to the valve 
stem E by right and left hand screws working in nuts 
let into the valves ; F F, rings in the steam chest cover, 
fitting close down on the back of the main steam valve, 
enclosing the space G, which is connected to the con- 
denser by the pipe H, for the purpose of balancing 
the valve. 

This cut-off can be worked by a separate eccentric, 
or from any part of the engine having a motion coin- 
cident with that of the piston. 

To alter the point of cutting-off, a wheel is on the 
end of the valve stem E, which, if turned in one direc- 
tion, will draw the valves closer together, and the 
openings will not be closed so soon, consequently the 
steam will follow the piston farther, i. e. cut off longer. 
To cut off shorter, the operation is reversed. 

OTHER KIND OF VALVES. 

Having explained the principles of the leading cut- 
offs, we will now take a glance at some of the most 
prominent steam and exhaust valves now in use; but, 
inasmuch as the student is supposed to understand the 
leading features of most of these, we will not devote 
much time to this part of our study. 

Figure 7 is a diagram of a double poppet valve, 
in which the rectangular space, a b c d is the open- 
ing to the cylinder ; A B, the steam valves, and C D, 
the exhaust valves. The object of this arrangement is 
to make the valve a balance valve. Thus the steam 
acting on the top of A and bottom of B, if they were 



OTHER KIND OF VALVES. 



31 



of equal size, an equilibrium would be established, but 
the valve B is made just small enough to slip through 



Fig. 7. 




Fig. 8. 



the upper seat, so that the difference in area serves to 
keep the valves fairly in their seats.* On the exhaust 
side the reverse is the case. The steam acts under C, 
and on top of D, the lower valve D is usually made 
the larger. In order to get D into its place, the upper 
seat is either made removable by being secured in its 
place by tap-bolts, or a hand-hole is cut in the side of 
the steam-chest, or, in some cases, it is passed in through 
the cylinder nozzle. 

Figure 8 is a diagram of the single poppet valve, 
in which A is the steam valve, and B, the exhaust. 
With these kinds of 
valves we see that we 
require considerable 
power to operate 
them by hand, as we 
have the full pressure 
of steam on the back 
of A, and also the 
exhaust on B; but 
when the engine is hooked on the pressure is in part 
balanced. On the steam valve this is occasioned at 
the time the valve is opened, by the exhaust valve 

* In some cases, tho areas of the valves are equal, and they are seated by their own weight 

3 




32 



OTHER KIND OF VALVES. 



being closed before the piston arrives at the end of the 
stroke, producing the pressure called cushion. And 
on the exhaust valve the pressure is reduced (at the 
time the valve is opened) by expansion. In some 
cases this pressure is but little above that in the con- 
denser. It is therefore obvious that these valves can 
be made to work with but little power from the engine. 
They also have the advantage of being easily made 
tight and occupying but little room. 

The disadvantage of working by hand, however, 
led to the adoption of the double poppet valve, the 
single poppet being the earlier invention. The double 
poppet valve is the one now almost universally used in 
American low-pressure river, or marine paddle-wheel 
engines. 

Figure 9 is a representation of what is termed 
" Hornblower's " valve, in which a ah h are the valve 



Fig. 9. 




seats; A A, the valve;. B, one of a number of cross- 
bars secured to the top of the valve, to which the 



OTHER KIND OF VALVES. 



33 



valve stem is attached. From the figure it will be 
seen that the only surface the steam has to act upon 
to keep the valve in its seat, is the upper edge, c c, of 
the valve ; it is therefore an equilibrium valve. 

Figure 10 is what is termed a box valve; a a 
are the parts communicating with the cylinder ; ft, 



Fig. 10. 




steam-pipe ; <?, the exhaust ; A A, the valve having an 
opening through its center communicating with ' the 
exhaust, c ; d d, packing. An inspection of the figure 
will show the operation of the valve. The object of 
this kind of valve is also to establish an equilibrium. 
Figure 11 is a longitudinal section, and figure 12 



Fig. 11 



/""(ft CONNECTS 
' CONDENSER 




a top view of what is termed the equilibrium slide. 



34 



OTHER KIND OF VALYES. 



Fig. 12- 



This valve lias a ring, A A, on the back of it, which 
being made steam tight, the 
pressure is taken off the space 
enclosed by the ring. The pres- 
sure is taken off the back of 
nearly all the valves of large en- 
gines now-a-days, fitted with the 
short slide, either in this way or 
by having the ring secured to 
the top of the chest, and the valve sliding under it. 

Figure 13 shows a slide valve AAA, having 
openings b b through it for the admission of steam ; 

Fig. 13. 





a a a is another valve sliding on the back of the 
valve A A A; a a a is the cut-off, which operates 
thus : The valve AAA being put in motion, and 
the cut-off valve lying loosely on its back, is carried 
with it until the end of the valve #, a, a, strikes the 
steam chest, when its motion is arrested, while the 
steam valve continues to move, the result is the clos- 
ing the opening 5, and the cutting off the steam. The 
sooner, therefore, the slide a a a strikes the chest, the 
sooner the steam is cut off. The point of cutting-off 
can be varied by having a screw running through the 



OTHER KIND OF VALVES. 



35 



chest, which can be moved further in 
against which the valve a a a strikes. 
With this arrangement it will be seen 
that the cut-off must close at further- 
est a little before the piston arrives at 
half stroke, or not close at all. This 
cut-off is applicable to horizontal sta- 
tionary engines. 

Fig. 1 4 is a piston valve, in which 
a a' are the openings into the cylin- 
der ; C, exhaust opening ; ABDE 
the valve packed at b o d e with 
rings or other packing. In the position 
shown in the figure, steam is being 
exhausted through the openings a' 
and C into the condenser, while steam 
is being admitted into the opposite 
end of the cylinder through the open- 
ing a. When the valve has its full 
throw in the opposite direction, steam 
will be admitted through the opening 
a! while it is being exhausted through 
«, and the opening F F through the 
valve and through C into the con- 
denser. 



or out 

Fig.14. 



and 



m 

tSka 



36 OTHER KIND OF VALVES. 

Figure 15 shows the long D slide, with the full 



Fig.. 15. 




opening for steam under the piston; Fig. 16, same 



Fie. 16, 




valve showing full opening for steam on top of the 
piston; Fig. 17, longitudinal section of the valve alone, 



Fig. 18. 



Fig. 17. 




P 



W777?777, 



mF*r 



^a 






and Fig. 18, cross section of the same. A is the steam 
pipe, B, the exhaust, C, packing to keep the steam and 
exhaust separate, steam being admitted into the chest 
or valve casing at A, fills the vacant space under and 
around the valve, but cannot escape past the ends 



OTHER KIND OF VALVES. 



37 



Fsg. 19 



owing to the packing C C ; and, when the valve is 
placed in the position shown in Fig. 15, steam is ad- 
mitted under the piston in the direction shown by the 
arrows, at the same time that it is exhausted through 
the upper opening, and — the valve being hollow — 
through it and pipe B into the condenser. When the 
valve is moved in the opposite direction, steam is ad- 
mitted above the piston in the direction shown by the 
arrows in Fig. 16, and exhausted 
through the lower opening directly 
through the pipe B to the condenser. 

This style of valve is in extensive 
use on English marine, and other 
engines. The objection to it is the 
friction, requiring several men to 
work the starting bar when the en- 
gine is operated by hand. 

Fig. 19 is a longitudinal section 
of the short D slide, and Fig. 20, an 
end view of the same. A A' are the 
openings into the cylinder ; B B, the 
communications to the condenser ; C, 
steam pipe. In the position shown 
in the figure, steam is being admitted 
through A into the cylinder, and ex- 
hausted through A' into the con- 
denser, € c is packing on the back of 
the valve. 



Fig. 2a 



< c ) 




38 



OTHER KIND OE VALVES. 



Fig. 21. 



fi* 



Fig. 22. 



Figure 21 is a view of the Worthington pump 

steam valve; figure 
22, the valve face, 
and figure 23, the 
valve seat. The fig- 
ures explain them- 
selves. In the or- 
dinary slide valve, 
when it is moved 
in one direction, 
steam is given to 
the piston in the 
same direction, but 
the object of this 
valve, as invented 
by H. E. "Worth- 
ington, of 1ST. York, 
is to cause it, when 
moved in one direc- 
tion, to give steam 
to the piston in the 
opposite direction. 
The valve being operated by an arm projecting from 
the piston rod, which strikes collars on the valve stem, 
renders it necessary that when the valve is moved in 
one direction, steam should be given to the piston in 
the opposite direction, in order to reverse its motion ; 
by this arrangement the intervention of levers is un- 
necessary, as the end is accomplished direct. 





VALVE 


















FACE 







Fig. 23. 



r 
i 






VALVE 




























1 








SEAT 











THE PITTSBURG- CAM. ■ 



39 



Fig. 24. 



1 > 

n 




C 

E 


\ 







\^ 


z^> 





Fig. 25. 



The Pittsburg Cam. — Figures 24, 25, and 26, show 

different forms of this 
cam. Like letters refer 
to like parts. A B C D 
is a yoke fitting over the 
cam a b c ; E is a rod 
attached to the valve 
stem. P, main shaft of 
the engine to which the 
cam is secured. It will 
be seen that by the revo- 
lution of the cam a b c, 
within the yoke ABC 
D, the rod E will be 
caused to move back and 
forth, and thereby open 
and shut the valve. 

Fig. 24 is a cam made 
to cut off at half stroke ; 
figure 26, J stroke, and 
figure 25 follows full 
stroke. The manner in 
which these cams are 
laid off is this. From 
the centre F, with a ra- 
dius dependent upon the 
stroke of the valve, de- 
scribe a circle, as shown 
partly in dots and partly 
in full lines in the fig- 
ures ; divide this circle 
into any convenient even 
number of equal parts, 
say sixteen ; then, supposing we wish to cut off at half 



XiV 


c 


/i r~ w v\ 




/ /*' X/ '- \ 


E 


/' i \ 




kffe^ 





\H^-- — ___!_. -"''V 






40 . OTHER KIND OF VALVES. 

stroke, taking figure 24, place one foot of the dividers 
having a radius equal to the diameter of the circle at 
C, and describe the arc terminating at 3, then move 
the foot of the dividers from c to a, and describe 
another arc terminating also at b ; then, with the same 
radius, and h as a centre, describe the arc a c ; the 
figure thus enclosed will be the required cam. It will 
be observed that, while the cam is traveling the dis- 
tance a 1 — that being an arc of a true circle — no mo- 
tion can be given to the valve, but while it travels 
from 1 to 2 the valve is opened and shut. Now, then, 
inasmuch as the piston moves from one end of the cyl- 
inder to the other for each semi-revolution of the cam, 
and inasmuch as the distance from a to 1 is the same 
as from 1 to 2, the valve remains necessarily closed 
during one-half of the stroke. 

In figure 25, as no part of the outline of the cam is 
concentric to the shaft F, the valve must be in motion, 
all the time the cam is in motion. In figure 26, as 
three-quarters of the semi-periphery of the cam is con- 
centric to the shaft F, the valve will remain closed 
during three-quarters of the stroke. Instead of making 
the points b sharp, as shown in the figures, they can be 
turned off, and, to retain the same dimensions on the 
cam, an equal amount added to the arc a c. Thus, 
taking figure 25, suppose we cut off the point of the 
cam to x y, and increase the lower extremity to H I, 
this will not alter the point of cutting off, but it re- 
duces the travel of the valve, and has the effect of 
keeping the valve stationary when wide open, while 
the cam travels through the arc x y. 



CHAPTER II. 

THE INDICATOR AND INDICATOR DIAGRAMS. 

The steam engine indicator is an instrument used 
for the purpose of exhibiting the performance of the 
steam engine. By its application to the steam cylinder 
we can ascertain the following particulars: Whether 
the valves are properly constructed and set; steam and 
exhaust passages of the right size ; whether the piston 
or valves leak ; the amount of vacuum or back pres- 
sure, and pressure of steam upon the piston ; the power 
of the engine ; power required to overcome its friction, 
and also to work any machinery attached to the same, 
&c. In truth, it is the stethoscope of the physician, 
revealing the internal working of the engine. 

The following description of the instrument and cut, 
Fig. 27, we take from Paul Stillman's Treatise on the 
Indicator. The cut shows the style manufactured at 
the Novelty Iron Works, New York city : 

A is a brass case enclosing a cylinder, into which a 
piston is nicely fitted. To the piston-rod a spiral 
spring is attached to resist the steam and vacuum 
when acting against it. B is a pencil attached to the 
piston rod. C is an arm attached to the case, and sup- 
porting a cylinder D, which may be caused to rotate 
back and forth — a part of a revolution in one direc- 
tion, by means of a line or cord £, attached to a suit- 
able part of the engine — and in the other by means of 



42 



THE INDICATOR AND INDICATOR DIAGRAMS 



Fig. 27. 



a strong watch spring within the cylinder D. Outside 
this cylinder is to be wound a 
paper, upon which a diagram 
will be made, by the combined 
action of the piston and paper 
cylinder, representing, by its 
area, the power exerted on one 
side of the piston during the 
whole revolution of the engine, 
//are springs to secure the paper 
to the cylinder ; g is a scale 
divided into parts corresponding 
to the pounds of pressure on the 
square inch. These divisions, 
for convenience of measuring the 
diagrams with a common rule, 
are generally made in some re- 
gular parts of an inch, as 8ths, 
lOths, 12ths, 20ths, 30ths; h is 
a cock by means of and through 
which it is connected with the 
engine cylinder. 

HOW TO ATTACH THE INDICATOR. 

Into whatever part of the 
engine it may be desired to ap- 
ply the indicator, there must 
first be inserted a small stop-cock, with a socket to 
receive the one connected with the indicator. The 
instrument is to be set into this in such a position that 
the line attached to the paper cylinder shall lead 
through or over the guide pulley toward the place 
whence it is to receive its motion. An extension of 
this line should be connected with some part of the 




THE IITOICATOR AND INDICATOR DIAGRAMS. 43 

engine, the motion of which is coincident with that of 
the piston, and which would give the paper cylinder a 
motion of about three-fourths of a revolution. If the 
engine is of the construction denominated beam or 
lever engine, and is provided with a " parallel motion " 
the parallel bar, or a pulley on the radius shaft, fur- 
nishes the proper motion; if otherwise, the beam 
centre may be resorted to. In the kind denominated 
square engines, the centre of the air pump gives it. In 
horizontal and vertical direct acting engines, it will 
frequently be found necessary to erect a temporary 
rock-shaft, or lever, connected with the cross-head. 
Particular care should be taken, when the power of the 
engine is to be estimated, that the motion communi- 
cated be perfectly coincident with that of the piston. 

In nearly all forms of the steam engine, the proper 
motion may be obtained by attaching a line to the 
cross-head, and passing it over a delicately constructed 
pulley, to the axis of which should be attached a 
smaller one, from which a line shall connect with the 
indicator. The proportional sizes of the two pulleys, 
of course, should be as the distance traveled by the 
piston to the length of motion given to the paper 
cylinder of the indicator. It will be necessary* to at- 
tach a strong spring to the axis of these pulleys, to 
produce the reverse motion promptly. In an oscillat- 
ing engine, it will be necessary that the indicator, with 
its fixtures, should be attached to the cylinder. 

As the paper cylinder cannot make more than 
about three-fourths of a revolution without disturbing 
the point of the pencil, it will be seen that the line 
communicating the motion must be of a definite length. 
It also require? to be readily connected and discon- 
nected. 



44 



THE INDICATOR AND INDICATOR DIAGRAMS. 



The indicator having been attached to the steam 
cylinder, the paper secured smoothly on the cylinder 
D, figure 27, and the length of the line e being ad- 
justed so that by the vibration of D it does not strike 
the stops, we will proceed to take a diagram, first- 
taking care to see that the paper cylinder D is so fixed 
that the springs ^/jf do not come in contact with the 
pencil B. The pencil B being adjusted so that it- 
touches lightly on the paper, throw it back and attach 
the hook on the line E to the line receiving motion 
from the engine ; then open the cock A, and allow the 
piston to work up and down several times, in order to 
heat and expand all the parts of the instrument. This 
being accomplished, turn the pencil on and take the 
diagram. Shut off the cock 7i, and apply the pencil 
again to the paper, and it will describe the atmospheric 
line. 

Figure 28 is a diagram taken from the U. S. S. 

Fig. 23 




i illl 

gl g | 8i| [l: 

■USES 




l 


*11 


— 


12 

10 

a 

4 
2 


a 

4 
6 
8 
10 
12 

14 f 7 



10) 204.5 



20.45 lbs. mean unbalanced pressure. 



THE INDICATOR AND INDICATOR DIAGPwAMS. 45 

Frigate " Powhatan," fitted with the double-poppet 
balanced valves, and Sickels' cut-off, on the 15th of 
January, 1854, while on the passage from Hong Kong, 
China, to the Loo-Choo Islands. At #, the piston of 
the indicator being at the bottom of its stroke, steam 
is admitted, forcing it up to b ; at b the cylinder upon 
which the paper is wound — having motion coincident 
with that of the steam piston — starts to turn, describ- 
ing the line be; at c the expansion valve closes, and 
the pressure therefore gradually falls to d, where the 
exhaust valve opens and the pressure falls suddenly to 
e ; the steam piston now starts on the return stroke, 
and the spring within the cylinder D, fig. 27, forces it 
back to the beginning a of the diagram. The line 
from a to b is called the receiving line ; from b to c the 
steam line ; from c to J, the expansion line ; d to <?, the 
exhaust; e to a, the vacuum line. The numbers in 
the vertical column on the right-hand side of the figure, 
are the pounds pressure ; 14.7 is the true vacuum line, 
6>, the atmospheric line, and 14, the initial pressure of 
steam above the atmosphere. The figures along the 
top line are the feet in length of the cylinder. It will 
be seen that the cut-off valve closed when the piston 
had traveled a very little beyond half stroke. The 
rounding at d and a is the lead and cushion on the 
exhaust. That is to say, the exhaust valve opened at 
d, before the piston arrived at the end of the stroke, 
and it also closed again at $, before the piston reached 
the other end of the stroke. Had there been no lead 
both of these corners would have been well defined. 

In order to calculate the power of the engine, the 
mean pressure on the piston must be known, and from 
no source but the indicator can it be accurately ascer- 
tained. The manner of arriving at this is simply by 



16 INDICATOR DIAGRAMS. 

taking the total pressure at different points and adding 
them up and taking the mean, as shown in fig. 28. 

Figure 28 is what would be termed among en- 
gineers a good diagram ; so is also figure 29, which we 
will take for a further elucidation of the subject. 

Fig. 29. 

Steam, 10 " Powhatan " stb. cylinder, bottom 

Vacuum, 27 Nov. 7, 1855, 10 a. m. 

Hot well, 106 Fahr. One engine and one wheel in 

Revolutions,.... 9.5 operation. 



Throttle, 8. Smooth 



■ea. 







ATMOSPHERIC LINE 



&/? 



/ \ i 

' \ 4 i 



i / 

v 1/ 



/ 



A 



L ^B 



It appears from this diagram, however, that the 
piston of the indicator worked rather tightly, which 
occasioned it to stick a little in some places, as is evi- 
denced by the steps in the expansion line, and also at 
a h in the vacuum line. If the piston of the Indicator 
become much scratched, similar effects will be produced. 
Great care should, therefore, be taken in its use, to see 
that neither the piston works too tightly nor too loose- 
ly ; for on the one hand it will stick, and thereby pro- 
duce an imperfect outline, and on the other hand will 
produce the same effect by exhibiting false vacuum and 
-expansion lines. 



INDICATOR DIAGRAMS. 47 

Should figure 29, instead of being as shown in full 
lines, have the lower right hand corner cut off as shown 
in dots at c d, the defect would have been that the ex- 
haust valve closed too soon — at c instead of e — occa- 
sioning excessive cushioning- With some engines, 
however, a large amount of cushioning is necessary to 
prevent them from thumping on the centres. 

Had the upper right-hand corner been rounding, as 
shown by the dotted line f g, the defect would have 
been that the steam valve opened too late. Had the 
exhaust corner been cut off, as shown by the dotted 
lines h £, the exhaust valve would have opened too 
soon ; but had it been in the form shown by the dot- 
ted line h I, it would have opened too late, and after it 
did commence to open, would move with too slow a 
velocity, preventing the free escape of steam, or the 
exhaust passages would have been too small, which 
would produce a similar effect to the valve opening too 
slowly. Had the steam line, instead of being parallel 
to the atmospheric line, fallen down in the direction 
m n, it would have shown that the throttle was par- 
tially closed, or the steam passages too small, prevent- 
ing the full flow of steam into the cylinder. 

Should there be excessive lead given to the steam 
valve, the line d m, instead of being at right angles to 
the atmospheric line, will have the top inclined to the 
right as from L to M. 

In taking a diagram for the purpose of estimating 
the power of the engine only, the atmospheric line is 
not necessary ; but in order to ascertain the vacuum 
it cannot be dispensed with, unless the indicator piston 
be forced down to the perfect vacuum and held there 
until that line be described. 

In a diagram taken from a non-conclensmo- engine, 

4 



48 INDICATOR DIAGRAMS. 

the atmospheric line will of course be entirely below 
it, owing to the back pressure occasioned from the 
passage of the exhaust steam through the openings 
and pipes. Had figure 29 been taken from a non-con- 
densing engine, A B would have been the atmospheric 
line. 

Figure 30 we have copied from Main and Brown's 
Treatise on the Indicator and Dynamometer. It was 

Fig. 30. 



C N 



taken from an engine fitted with the long D slide. 
There are two defects exhibited in this diagram ; the 
steam communication is opened too late and the ex- 
haust too soon. At C the exhaust closes, causing the 
steam to be compressed to O, when the piston having 
arrived at the end of the stroke starts on its return, 
and the pressure falls to O' ; at O' steam is admitted, 
causing the line O' A to be traced ; at B the exhaust 
opens long before the piston arrives at the end of the 
stroke, allowing the steam to escape too soon. The 
hook, as shown at O, would only be made in very 
aggravated cases, where the steam is very much be- 
hind time. 



INDICATOR DIAGRAMS. 



49 



Fig. 31 is obtained from the same source as figure 
30. In this case the engine was working as a non- 



Fig. 31. 



C v c 



condensing engine with a very low pressure of steam. 
The exhaust closes at A, causing the pent-up steam to 
be compressed to B, where the steam valve opens, 
and the pressure in the cylinder being greater than 
that in the boiler, immediately falls to C. The hook 
at C is occasioned by the momentum of the indicator 
piston. At D the cut-off closes, causing the steam to be 
expanded to E, below the atmosphere. At E the 
exhaust valve opens and the pressure rises up equal to 
the back pressure, causing the loop on that corner of 
the diagram. 

Figure 32 is a diagram drawn from memory, from 
one of a non-condensing FlG< 85L 

engine that was once 
shown the author, with 
the request that he 
point out the defect in 
the engine from which 
such a diagram was 
taken. At first we did 
not see any reason why 
the pressure should rise from b to <?, for supposing the 
exhaust to open at #, there could be no reason why 
the pressure should rise beyond d, the amount of back 
pressure on the opposite side of the piston. After 
looking at it a little closer, however, it occurred to us 




50 



INDICATOK DIAGEAMS. 



that sucli a diagram could be formed from a slide valve 
engine, and in this manner : Steam being admitted in 
the usual way until the piston arrived at a, the inde- 
pendent slide cut off the steam, whence it was expanded 
to the point b ; at b — the steam valve having neither 
lap nor lead, and consequently still open — the cut-off 
again opened the communication with the cylinder, 
admitting fresh steam, which caused the line b c to be 
traced, partaking of the motion of the steam and piston. 
At c the steam is shut off by the steam valve itself, 
and the exhaust opened, the pressure therefore falls 
from that point to d } and the exhaust line is traced. 
In a non-condensing engine diagram, where of course 
there can be no vacuum line, the line from c to e in- 
clusive is termed the exhaust. 

A perfect Diagram. — According to the law laid 
down by Marriotte, which we have previously studied 
under the head of expansion of steam, the expansion 
curve of an indicator diagram should be a true hyper- 



Fig. 33. 




bolic curve, were there no extraneous circumstances to 
cause it to be otherwise ; but unfortunately in practice 
this perfection is not attainable were Marriotte's law 



INDICATOR DIAGRAMS. 51 

literally true, owing to the time required for steam to 
enter and leave the cylinder clearance of piston, space 
in nozzles between the valves, leakage of valves, piston 
condensation in the cylinder, &c. Fig. 33 is intended 
to show a perfect diagram, having all the corners "well 
defined and the expansion line a true hyperbolic curve. 
From this figure we purpose explaining the manner of 
laying out a true hyberbolic curve. Let A E be the 
true vacuum line, and B C the steam line. Divide 
A E into any number of equal parts, and erect the 
perpendiculars A B, 1 1', 2 2', &c. ISTow we see that 
the steam follows the distance A, 2, or two divisions 
before it is cut off the length of the ordinate 3 3', 
being three divisions from the commencement should 
be | of 2, 0', the length of 4 4', £ ; of 2, C ; of 5 5' f ; 
of 6 6' |; of 7 T -f; of E D, f. With the lengths 
of all these ordinates marked on the diagram drawn 
through the points 3', 4', 5', 6', f , &c, the line C D, 
and you have the required curve. 

An experienced engineer can tell at a glance 
whether an engine is in good working order from its 
diagram ; but nevertheless, in most cases it would be 
well to draw the true curve, in order to ascertain how 
much the actual one differs from it, for by this means 
we can ascertain, while under way, whether the valves 
or piston leak ; but in drawing the true curve, the 
clearance of the piston and space in the nozzles, <fcc., 
must be ascertained, and that much added to the length 
of the diagram, in order to obtain the curve accuratelv. 
Thus, supposing this space to be equal in capacity to 
six inches in length of the cylinder, make the diagram 
six inches longer than it actually is, and proceed in the 
manner we have shown. 

Should the steam valves leak while every thing 



52 



INDICATOR DIAGRAMS. 



else remains tight, the termination of the expansion 
line will be too high, and if the exhaust valves or pis- 
ton leak, it will be too low, — allowance being made 
for condensation in the cylinder. 



Fig. 34. 



Steam 10 lbs. 

Rev 9 

Vac 26 

Hot well 100° 

Throttle wide. 



" Powhatan " stb. cylinder-top. 
February 13th, 1854. 




Figures 34 and 35 are two diagrams taken from 
the U. S. Steamer Powhatan, on the 13th of February, 
1854 ; 34 was taken about ten minutes after 35. In 
both of these figures we have the true hyperbolic 
curves drawn in, with and without taking the clear- 
ance, &c, into account. The upper curve in small 
dots is the true curve, when the clearance, &c, is 
taken into consideration, and the lower one in large 
dots is the true curve without reference to the clear- 
ance, &c. In figure 35, where the steam was cut off 
at a very early part of the stroke, the importance of 
taking the clearance, &c, into consideration, is very 
conspicuous. The dotted lines on the right of these 



INDICATOR DIAGRAMS. 53 

diagrams show the amount they are lengthened by 
adding the clearance, space in nozzles, <fcc., to them. 

Fig. 35. 

Steam 8^- lbs. " Powhatan " stb. cylinder-top. 

Rev 6 February 13th, 1854. 

Vac 26^ 

Hot well 82° 

Throttle wide. 




From a casual inspection of these diagrams, they 
seem to present an anomaly that at first is difficult to 
solve. Thus, in figure 34, the termination of the true 
expansion curve, considering clearance, &c, is about 
one pound above the actual curve, whereas in figure 
35 it is two pounds below it. The first would indicate 
that the exhaust valves or piston leaked, and the 
second that the steam valves leaked, while the exhaust 
valves and piston were tight. Now, then, since one 
was taken only about ten minutes after the other, it is 
not at all probable that this sudden change was 
brought about in that short space of time ; hence we 
must look for some defect in the engine that would 
occasion it. We account for it in this way : In the 



54 INDICATOR DIAGRAMS. 

first case the steam valve leaked, and also the steam 
piston, but the piston leaked to a greater extent than 
the valve, that is to say, more steam passed through 
the piston and into the condenser from the leakage of 
the piston than entered the cylinder from the leakage 
of the valve ; therefore, the actual curve must fall be- 
low the true curve. In the second case, the steam 
valve also leaked, but the pressure on the piston fell 
so rapidly, from expansion, that it became too low to 
force a passage through the piston, the elasticity of the 
packing being sufficient, in this case — though not in 
the other, where it had a greater pressure to sustain — 
to keep it tight; hence, the true curve in this case 
must be below the actual curve, agreeing precisely 
with the conditions of the figures. 

There is, however, another thing which would pro- 
duce diagrams similar to those before us, and which 
most probably caused the formation of these, viz., leak- 
age about the cylinder heads. Thus, supposing the 
stuffing box, for instance, to leak. So long as the 
pressure in the cylinder remained above the atmo- 
sphere, steam would blow out, occasioning the curve 
to fall ; on the other hand, when cutting off short, the 
pressure in the cylinder would soon fall below the 
atmosphere, and air would enter, causing the curve to 
rise, exactly as shown in the figures. 



INDICATOR DIAGRAMS. 55 

'Fig. 36 is a diagram taken from the U. S. Steamer 
u San Jacinto," fitted with Allen & Wells' cut-off. 

Fig. 36. 

Steam in boilers ll^lbs. November 7th, 1855, 1 If A. M. 

Revolutions 18 After Engine, inboard end. 

Vacuum 25^- Coal 18 tons in 24 hours. 

Hot well 104° 

Throttle 4 holes open. Scale = Vic 




From inspection of the expansion curve of this dia- 
gram, it appears that this cut-off does not close so 
quickly as Sickel's, occasioning the corner a to "be 
more rounding. 

Fig. 37. 

Steam in boilers 9 lbs. "Powhatan," Feb. 13th, 1854. 

Revolutions 5 stb. cylinder bottom, working by hand. 

Hot well 100° 

Throttle 4 




Figure 37 is a diagram showing the operation of 



56 



AIR-PUMP DIAGRAMS. 



the valves while working by hand. This valve ex- 
hibits large cushioning and steam lead, the exhaust 
valve closing at a, and the steam valve opening at Z>, 
so that the engine actually passed the centre against a 
pressure of 6^ lbs. above the atmosphere. 



Steam 16.5 lbs. 

Revolutions 9.25 

Hot well 106° 

Vacuum gauge out of order. 



" Powhatan " stb. air-pump, 10.50 A. M. 
January 18th, 1854. 




Calculated for Vs full of water. 

Number 1 is a diagram taken from the " Powhat- 
an's " starboard air-pump. The Powhatan's air-pumps 
are of the lifting kind, and the piston fitted with one 
large brass conical valve. We will explain the dia- 
gram. At a, the piston being at the bottom of the 
stroke, starts to rise, compressing the air and vapor 
above it, until it arrives at 5, at which place a sudden 
discharge of air and vapor seems to have taken place, 
and the pressure fell to <?, from which point the pres- 
sure again gradually rose until it arrived at d, where 
the water began to be delivered and continued to the 
end of the stroke. 



AIR-PUMP DIAGRAMS. 



57 



Attached to the top of the air-punips is a pipe, run- 
ning down into the bilge, for the purpose of pumping 
off the bilge water. Where this pipe is attached to 
the pump is fitted a valve, operating like an ordinary 
check valve, a handle being made to screw down on 
the top of it to keep it firmly in its seat, when there is 
no water in the bilge. 



Steam 15 lbs. "Powhatan" stb. air-pump, 10.55 A. M. 

Revolutions 10 January 18th, 1854. 

Hot well, 106° 

Vacuum gauge out of order. 




Resistance of vapor and water in Air-pump 



= (6.6 -f 312 x .0969=) .6697 lb. per square inch of steam piston. 
Calculated for 1 5 full of water. 



There being no water in the bilge at the time No. 1 
was taken, JSTo. 2 was taken five minutes after, for the 
purpose of ascertaining what effect the opening of this 
valve and admitting air would produce. It shows 
that no extra power, from the admission of this air, 
Avas required to work the pump, the average pressure 
being about the same as in No. 1, and that the vacuum 
in the pumps at no time was more than 4 \ lbs. There 
was no alteration in the vacuum, as shown by the 
gauge, however attached to the condenser, and the 
engines continued to work in the same manner as be- 



58 



AIR-PUMP DIAGRAMS. 



fore the bilge valve attached to the air-pump was 
opened. 

Steam 15lbs. " Powhatan " port air-pump, 11.6 A. M. 

Revolutions 10 January 18th, 1854. 

Hot well 108° 

Vacuum gauge out of order. 




Resistance of vapor and water in Air-pump 



= (6.46 -j- .223 x .0969 =) .6476 lb. per square inch of steam piston 
Calculated for 2 /t full of water. 

Nos. 3 and 4 were taken in the same manner from 
the port air-pnmp a few minutes after 1 and 2 were 
taken from the starboard pump. 

In these diagrams the pressure at the termination 
of the up stroke, it will be seen, is about 2| lbs. per 
square inch above the atmosphere, which is due to the 
height of the level of the water surrounding the ship 
above the top of the air-pump. The pressure increased 
to between 1 and 8 lbs. per square inch, as shown in 
other parts of the diagram, is occasioned by the fric- 
tion of the water and vapor through the delivery pipes 
and valves. The slanting off in the diagram, No. 1, 
from x to y, we think partly owing to two causes : 
First, the decreased velocity of the piston as it ap- 



AIR-PUMP DIAGRAMS. 



59 



proaclies the end of its stroke does not expel the water 
with such force, and hence there is not so much fric- 

Steam 15 lbs. " Powhatan " port air-pump, 11.15 A. M. 

Revolutions 10 January 8th, 1854. 

Hot well 108° 

Vacuum gauge out of order. 




Resistance of vapor and water in air-pump 



= (8.16 -f- 223 x .0969=) .8123 lbs. per square inch of steam piston. 
Calculated for y 7 full of water. 

tion ; but this would not occasion the slanting off from 
h to z on the return stroke ; and secondly, there- 
fore, we are inclined to think that the string slipped or 
stretched a little from x to y y and recoiled again to its 
original place from h to z. 

We will now proceed to ascertain the 

Poiver required to work the Air-pump. 

Ascertain the capacities of the steam cylinder and 
air-pump, by multiplying the areas of their cross-sections 
by the lengths of their strokes, and divide the latter 
by the former, which will give the ratio of the cylinder 
capacity to that of the air-pump. But the air-pump 
makes but one delivery stroke to every tivo strokes of 
the steam piston, consequently divide this ratio by 
two, which will give the coefficient for our present 



60 POWEE REQUIRED TO WORK THE AIR-PUMP. 

calculation, and this coefficient multiplied by the mean 
pressure per square inch of air-pump piston — which 
can be ascertained from an indicator diagram — will 
give the mean pressure per square inch required to 
expel the air and vapor. 

This of course must be augmented by the weight 
of the water raised. 

The indicator diagram will show very nearly at 
what part of the stroke the pump begins to deliver 
the water, and therefore what fraction of the pump is 
filled, from which can be easily ascertained the number 
of cubic feet of water lifted ; and this number multi- 
plied by 64.3 or 62.5, as the vessel may be running in 
salt or fresh water, will give the number of pounds. 
And the number of pounds of water lifted, divided by 
the area of the air-pump piston, and multiplied by the 
coefficient before obtained, will give the pressure per 
square inch of steam piston required to expel the water 
from the pump. 

The sum of these results will give the pressure per 
square inch of steam piston required to work the air- 
pump independent of friction, an amount that is usually 
estimated. 

Example: The capacity of the "Powhatan's" cyl- 
inder, i. e., the space displaced by the steam piston per 
stroke, is 267.25 cubic feet: ditto in air-pump, 51.8 
cubic feet ; proportion of steam piston displacement to 
that of half of air-pump piston displacement, 1.000 to 
.0969; area of air-pump piston, 2134 square inches. 
The pump was filled \ full of water, as shown by dia- 
gram No. 1, and the mean pressure throughout the 
stroke was 6.5 lbs. per square inch ; hence, 6.5 x .0969 
= .62981b. per square inch of steam piston resistance 
from vapor in air-pump, and .312 X .0969 = .0302 lb. 



POWER REQUIRED TO WORK THE AIR-PUMP. 61 

per square inch of steam piston resistance from the 
weight of water lifted ; total = (.6298 + .0302 =) .66 
pounds per square inch of steam piston, required to 
work the air-pump, independent of friction. 

Now, supposing the mean unbalanced pressure on 
the steam piston per square inch to have been 20 lbs., 
we have 20 : .66 : : 100 : 3.3 per cent, of the total 
power of the engine required to work the air-pump. 



CHAPTEE III. 



THE HYDPwOMETEE. 



Fig. 42. 



r~\ 



The Hydrometer is an instrument used for the 
purpose of determining the specific gravi- 
ties of liquids. When applied to the 
water of marine boilers, it indicates the 
amount of saline matter the water con- 
tains. Figure 42 shows the kind of hy- 
drometer usually used on board Ameri- 
can steamers. The lower globe is filled 
with shot, or other weighty substance, 
for the purpose of keeping the instru- 
ment upright. When the hydrometer is 
placed in fresh water, the point O stands 
even with the surface of the water ; when 
placed in water containing one pound of 
saline matter in thirty-two pounds of 
water, it stands at )L 2 ; when the water 
contains two pounds of saline matter in 
thirty two pounds of water it stands at 
% 2 , and so on. So that by placing this 
instrument in a small quantity of water, 
drawn from the boilers at intervals, it 
will show the exact density, by which 
we know how to regulate the bio wing-off. 

In the boilers of sea-going vessels the 
water is usually carried from 1 % to 2 per 
hydrometer, i. e., from the point a to b, 
figure 42. In the Gulf of Mexico, how- 
ever, in the vicinity of the Florida reefs, where the 







THE HYDROMETER. 63 

water is impregnated with an unusual amount of lime, 
it is found not to be prudent to carry it beyond 1 )' 2 . 

The hydrometer, when made for a certain temper- 
ature, is not adapted to any other, but the water 
should be allowed to cool down to the temperature 
marked on the hydrometer before observing the indi- 
cation, and for this purpose it becomes necessary also 
to use a thermometer. The hydrometers used in this 
country are usually graduated for a temperature of 
200° Fahr. We can allow, however, for a few degrees 
either above or below this figure, without appreciable 
error — a difference of 10° in temperature making a 
difference of about an eighth of % 2 in the scale. Thus, 
supposing the water to be at a temperature of 210°, 
and the hydrometer graduated for 200° to stand at «, 
or 1%, the actual density of the water will not be 1%, 
but l 7 / 8 , or halfway between a and h. On the other 
hand, if the temperature be 190°, and the hydrometer 
stand at 1%, the true density will be 1%. Neverthe- 
less, in practice, it is always best to allow the water to 
cool to the temperature for which the hydrometer is 
graduated, whenever it can be done without the waste 
of too much time. 

It will be observed that the divisions on the scale 
are not of equal lengths. Thus : the distance from O 
to y 32 is greater than from % 2 to % 2 , and from % 2 to 
%2j greater than from % 2 to % 2 , and so on. The reason 
of this can be explained in this manner : When the . 
instrument stands at O, the two bulbs, and all the 
tube below O, of course, are immersed, having the 
weight due to the length of the tube only above O to 
support. When it rises to % 2 it has more weight to 
support, from the fact of there being more tube out 
of water, and it also has less bulk immersed ; at % 2 it 



64 LOSS BY BLOWING OFF. 

has still more weight to support, while there is still 
less of the instrument immersed, and so on down to 
the bottom of the scale, occasioning the lengths of the 
divisions to "become less and less. 

The proportional quantity of saline matter con- 
tained in sea water, at different localities, varies very 
considerably, as will be seen in the following 

TABLE : 



Baltic Sea, . 


152 


Mediterranean, . 


Black Sea, 


• *v 


Atlantic at Equator. 


Arctic Sea, 


1 

33 


South Atlantic, . 


Irish Sea, 


• A 


North Atlantic, 


British Channel, 


25 


Dead Sea, . 



LOSS BY BLOWING OFF. 

When water contains 3 per cent, by weight of sa- 
line matter, no deposit takes place at the boiling 
point ; — under atmospheric pressure or 212° Fahr. 
When it contains 10 per cent, it makes a deposit of 
lime, principally sulphate, and at 29, 5 per cent, com- 
mon salt. 

The precise saturation, however, at which deposit 
commences to take place is not well established, but 
there is one thing which is well known, and that is, 
the higher the temperature of the water, the greater 
will be the deposit, and from this we conclude that 
common sea water would deposit a portion of its saline 
matter if heated to a sufficiently high temperature. 
The reason of the increase in deposit, as the tempera- 
ture is increased, is probably owing to the expansion 
of the water, or the separation, as it were, of the par- 
ticles. 

Water carried at a density that would cause no 



LOSS BY BLOWING OFF. 65 

deposit at a temperature of 220°, would make consid- 
erable deposit at a temperature of 260° or 270°; and 
this is the reason why we are limited to comparatively 
low steam in boilers using sea water. Independent of 
the saving of the loss by blowing off, repairs to boilers, 
labor of cleaning them, <fcc., this is a powerful reason why 
inventive genius should endeavor to bring forth a relia- 
ble fresh water condenser, and why steamship owners 
and others, having it within their power, should encour- 
age all such attempts, from the fact of the great advan- 
tage to be derived from carrying high pressure steam, 
and using the expansive principle to its fullest extent. 

To the minds of those who cannot clearly see that 
an increase of temperature occasions an increase in de- 
posit, a practical demonstration can be obtained by 
examining the crown sheets, and other parts of marine 
boilers, subject to the highest temperature, where it 
will be found the largest deposit takes place. 

The deposit of lime, or " scale," as it is technically 
termed, on the heating surface of boilers, being nearly a 
non-conductor of caloric, prevents a large portion of the 
heat from entering the water, allowing it to escape up, 
the chimney, and is therefore lost ; and, if the deposit 
of scale be large, the metal of the boiler, being no 
longer protected by the water, becomes over-heated 
and " burnt." To prevent these results, a portion of 
the water is extracted periodically, or continuously, 
by the brine pump, or is discharged by the blow-off, 
in order to keep the density of the water below the 
point at which any serious deposit may take place. 
But as all the water discharged from the boiler has 
first to be heated, and as it is replaced by water of a 
lower temperature, a loss of heat (which is virtually a 
loss of fuel) is occasioned thereby. This is technically 



66 LOSS BY BLOWING OFF. 

termed " loss by blowing off," and we shall proceed to 
illustrate tlie manner of calculating it. Take an ex- 
ample. 

Supposing the density of the water entering the 
boiler to be -g-V, and that of the boiler to be maintained 
at ¥ 2 ¥ , there will be one part converted into steam, and 
one part blown out. Supposing also the temperature 
of the water entering the boiler to be 100° Fahr., and 
the temperature of the water in the boiler to be 248° 
Fahr., we have all the data required. 

Referring to Regnault's experiments, (page 9), we 
see that the total heat in steam having 248° for the 
sensible heat, is 1189.58°, now then 

1189.58° = total heat; 

100.00° = temperature of the water entering the 

boiler ; 

1089.58° = heat required from the fuel for the 
water to be evaporated ; 

248° = temperature of the water in the boiler ; 

100°= " " " entering " 



148° = heat lost by blowing off. 

Therefore, since one part (requiring 1089.58°) is 
converted into steam, and the other part (requiring 
148°) is blown off, the total heat required of the fuel is 
(1089.58° + 148°=) 1237.58°; and as 148° of this is 
blown off, we have 1237.58 : 148 : : 100 : 11.95 + per 
cent, loss by blowing at the above density and tem- 
perature. 

If the water had been carried at a density of If 
per hydrometer, one part would have been blown off 
as before, but only three-quarters part would have 



LOSS BY BLOWING OFF. 67 

been converted into steam, hence we would have pro- 
ceeded thus — 

1189.58° 
100.00° 



1089.58° 
.75° 



817.1850° = heat required from the fuel for the 
water to be evaporated. 

248° 
100° 



148° = heat lost by blowing off. 

Therefore (817.185 + 148 =) 965.185 : 148 : : 100 : 
15.33 + P er c ent. 

And had the water been carried at a density of 
3, L e. -3V? ^ wo parts would have been used for steam 
and one part blown off, hence the following : 

1189.58° 
100.00° 



1089.58° 
9° 



2179.16° = heat required from the fuel for the 
water to be evaporated. 

248° 
100° 



148° = heat lost by blowing off. 

Therefore (2179.16° + 148°) = 2327.16° : 148 : : 100 : 
6.35 per cent., and so on for any density. These per 



68 GAIN BY THE USE OF HEATEES. 

cents, are the losses in fuel, combustible, minus that 
lost from radiation and heated gases passing up the 
chimney. 

The above calculations apply only to cases where 
the water enters the boiler at a density of -^ ; should 
it enter at a lower density, the loss will be less, or a 
greater density more, because to retain the water iq 
the boiler at the density assumed in the above ex- 
amples, there would either have to be a less or greater 
quantity blown off than we have considered to be the 
case. 

In order not to lose entirely all the heat in the 
water blown off, some boilers are fitted with heaters, 
or as they are sometimes termed incorrectly, " refrige- 
rators." These are a series of pipes surrounded by the 
feed water, and through which the water leaving the 
boilers has to pass ; by this means the temperature of 
the feed water is considerably increased before it 
enters the boiler. The following will illustrate 



THE GAIN BY PUMPING WATER INTO THE BOILER AT AN 
INCREASED TEMPERATURE. 

For this purpose two examples will be sufficient, 
and we will commence with the first one given above 
in the calculation on the loss by blowing off; viz. 
steam, 248° ; feed water, 100° ; and density, -fy. Now 
suppose by the application of the heater, the feed- 
water, instead of entering the boiler at 100°, is made 
to enter at 150°, what will be the saving in fuel by its 
application ? 



GAIN BY THE USE OF HEATEBS. 69 

Solution. 

1189.58° = total heat in the steam ; 
100.00° = temperature of the feed water; 



1089.58° = heat required from the fuel to evapo- 
rate one part of water ; 
248° hz temperature of the water blown off; 
100°= " " feed water: 



148° = heat lost by blowing off; 
and 1089.58° + 148° = 1237.58 = total heat required 
from the fuel where the water is pumped into the 
boiler at 100°. Let us now see what the total heat 
will be when the water is pumped in at 150°, and the 
difference between these results will be, of course, the 
saving 

1189.58° == total heat in the steam; 
150.00° = temperature of the feed water ; 



1039.58° == heat required from the fuel to evapo- 
rate one part of water ; 
248° = temperature of the water blown off; 
150°= « " feed water; 



98° = heat lost by blowing off; 
and 1039.58° + 98° -= 1137.58° = total heat required 
from the fuel when the water is pumped into the boiler 
at 150°. Therefore 

1237.58° 
1137.58° 



100°= saving in degrees 



whence 1237.58° : 100° : : 100 : 8.08 per cent. That is 
to say, if without the heater the boilers consumed 100 



TO GAIN BY THE USE OF HEATERS. 

tons of coal per day, with it they would produce the 
same quantity of steam with 91.92 tons. 

Example 2d. 

Suppose that the density of the water in Example 1 
was If, and all the other conditions to remain unalter- 
ed, what would be the saving in that case ? 

Solution. 

1189.58° = total heat in the steam; 
100.00° =± temperature of the feed water ; 



1089.58° = heat required from the fuel to evapo- 
rate one part of water ; 
.75° = part of water evaporated ; 



817.185° == heat required from the fuel for the 
water that is evaporated ; 
248° = temperature of the water blown off ; 
100°= " " feed water; 



148° = heat lost by blowing off; 
817.185°+ 148° = 965.185° = total heat required from 
the fuel when the water is pumped into the boiler at 
100°. 

1189.58° = total heat in the steam-, 
150.00° = temperature of the feed water; 



1039.58° = heat required from the fuel to evapo- 
rate one part of water ; 
.75° = part of water evaporated; 

779.685° = heat required from the fuel for the 
water that is evaporated ; 



INJECTION WATER. 71 

248° = temperature of the water blown off; 
150°= " " feed water; 



98° = heat lost by blowing off; 

779.685° + 98° = 877.685° == total heat required from 
the fuel when the water is pumped into the boiler at 
150°. Therefore 

965.185° 

877.685° 



87.5°= saving in degrees. 

Whence 965.185° : 87.5° : : 100 : 9.06 per cent. And 
in this manner the calculation can be made for any 
density and temperature. 

In making calculations on the theoretical saving 
from the use of the heater, we have seen some engineers 
who calculate the loss by blowing off without it, and 
again with it, and take the difference between these 
two results for the saving ; but it will require but 
little reflection for any one at all conversant with such 
subjects, to perceive the error of this mode of calcu- 
lation, as it takes no cognizance whatever of the extra 
heat given to that portion of the water which is evap- 
orated. The mode of calculation given above is the 
only correct one, as it takes into consideration all the 
elements. 

INJECTION WATER. 

After the steam has performed its duty in the 
cylinder, and been exhausted into the condenser, a cer- 
tain amount of cold water is admitted into that vessel 
for the purpose of condensing it, and this quantity 
depends upon the temperatures of the water and the 
steam. We will take an example. 



72 EVAPORATION. 

Suppose the temperature of the injection water to 
be 60° ; steam as it enters the condenser, 212° ; and 
water in the condenser, 110°. Required the proportion 
of injection water to the water evaporated in the 
boiler : 

Solution. 

1178.6° = total heat in the steam at the sensible 
temperature of 212° ; 
110.0° = temperature of the water after conden- 

sation ; 

1068.6° = heat to be destroyed ; 

110° = temperature of the water after conden- 
sation ; 
60° = temperature of the injection water, 



50° difference. 
Now then we see that we have 1068.6° of heat to 
be destroyed, and only 50° to do it with, therefore we 
must make up this difference in quantity ; hence 1068.6° 
—50° = 21.372 times the evaporated water to be ad- 
mitted into the condenser to condense the steam and 
retain the condenser at the temperature of 110°. 

EVAPORATION. 

Among the important elements to be ascertained 
in the performance of the steam engine, is the quantity 
of water evaporated in the boilers per unit of coal, or 
other fuel. In sea boilers using salt water, one pound 
of coal evaporates from 4 to 9 pounds of water, de- 
pendent upon the quality of the coal, the construction 
and cleanliness of the boilers. Those boilers are of 
course the best which evaporate the largest quantity, 
and hence the importance of knowing the exact per- 
formance of each boiler, as well as of the different kinds 



EVAPORATION. 73 

of fuels used in the same. To secure this desirable end 
we proceed thus : 

Ascertain from indicator diagrams the fraction of 
the cylinder filled at each stroke, from which, know- 
ing the diameter of the cylinder, we ascertain the 
number of cubic feet of steam required to fill that 
space, and to this we add the space in nozzles, clear- 
ances, &c, which gives the number of cubic feet of 
steam used per stroke ; and the number of cubic feet of 
steam used per stroke, multiplied into the number of 
strokes per hour, and divided by the relative volumes 
of steam and water, at the pressure the steam is admit- 
ted into the cylinder, gives the number of cubic feet 
of water evaporated per hour, and the number of cubic 
feet of water evaporated per hour, multiplied by 64.3, 
(the weight in pounds avoirdupois of one cubic foot of 
sea water,) and divided by the number of pounds of 
coal used per hour, gives the number of pounds of water 
evaporated per pound of coal, provided there is no 
blowing off done ; but wherever there is blowing off, 
this last result has to be increased to the extent of the 
loss by blowing. 

Suppose for instance, proceeding in the manner 
given above, we find 6 lbs. of water to be evaporated 
per pound of coal ; and the loss by blowing off to keep 
the water at the proper density to be 15 per cent., 
the remaining 85 per cent, is that which evaporates 
the 6 lbs. ; hence 85 : 6 : : 100 : 7.06 lbs. of water evap- 
orated per pound of coal. 

Example. — Suppose you have a cylinder 70 inches 
diameter by 10 feet stroke ; the initial pressure of 
steam in the cylinder 24.5 lbs. per square inch, in- 
clusive of the atmosphere, cut off at \ from commence- 
ment of stroke; clearance, &c, 10 cubic feet; revolu- 



74 EVAPOKATIOST. 

tions, 15 per minute ; coal consumed per hour, 1,500 
lbs. ; water carried at If per hydrometer ; temperature 
of feed water, 107° Fahr. ; required the number of 
pounds of water evaporated per pound of coal : 

Solution. 

70 2 X .7854 x 10 1Q = ?6 812g cubic feet of 
144 4 

steam used per stroke; and 76.8125 X 15 X 2 X 60 — 
138262.5 cubic feet of steam used per hour. 

The relative volumes of steam and water at the 
pressure of 24.5 lbs. are 1064 to 1 ; hence 

i QQ9A9 5 

— — ^r^- X 64.3 ~ 1500 = 5.57 lbs. of water per pound 
1064 

of coal, neglecting the loss by blowing off; but, ac- 
cording to the conditions of the example, the loss by 
blowing off is found to be 14.1 per cent., the remain- 
ing 85.9 per cent, is that therefore which evaporated 
the 5.57 lbs. of water : hence the true evaporation is 
found to be 85.9 : 5.57 : : 100 : 6.48 lbs. of water per 
pound of coal. 

The above calculation takes no cognizance of the 
leakage of the valves, loss by radiation, or condensa- 
tion in the cylinder, pipes, &c. ; hence the results show 
too small, but it is the only standard of comparison. 

Some parties calculate the evaporative power of 
boilers by measuring the quantity of water pumped 
into them during any given time, and also the quantity 
of coal consumed in the furnaces during the same time, 
and dividing the weight of the former by the latter, 
which they conceive gives the weight of water evapo- 
rated per unit of coal. Upon first sight this mode of 
operating appears very simple and correct ; but unfor- 
tunately, notwithstanding its simplicity, the results are 



STEAM AND VACUUM GAUGES. 75 

never accurate, the evaporation being always shown 
too large, for the very simple reason, that all the water 
pumped into a steam boiler is never evaporated. All 
boilers, and pipes, and cocks attached thereto, leak 
more or less, and sometimes boilers foam, occasioning 
water to be worked into the cylinders, and as, accord- 
ing to this mode of calculation, all water escaping by 
this means is supposed to be evaporated, the result 
manifestly cannot be correct. 

Steam and vacuum Gauges. 

As applied to the marine steam engine, the mer- 
curial steam and vacuum gauges are the most common, 
though of late years there have come into use a variety 
of metallic gauges, many of which, from the little 
attention they require, appear to be very well adapted 
to the purpose for which they were intended. 

The most prominent of these are " Schaffer's," 
"Hearson's," "Schmidt's," " Ashcroft's," "Eastman's," 
" Stubblefield's," an <l "Allen's." In the first three, 
the spring is a thin corrugated plate, upon which the 
steam acts, communicating motion to a hand or pointer 
which moves around a circular disc marked in pounds : 
the spring in Ashcroft's gauge is a bent tube, which 
the elasticity of the steam tends to straighten. East- 
man's gauge is a combination of springs and levers. 
As these gauges are all constructed on the same prin- 
ciple, viz., the elasticity of metal, we shall not stop 
here to describe them, as it is more directly our object 
to deal with principles, rather than mechanical ar- 
rangements, which are the chief peculiarities of these 
gauges. "We will pass on to the mercurial closed top 
vacuum gauge. 



16 



STEAM AND VACUUM GAUGES. 



abed, figure 43, is a basin filled 
with mercury up to the point A ; the 
tube B is also filled with mercury. 
The pipe e communicates with the 
condenser, and when that vessel is 
filled with air of the atmospheric 
pressure, the surface of the mercury 
in the basin is pressed with a pres- 
sure of about 15 lbs. per square inch, 
causing the tube B to remain filled ; 
but when a partial vacuum is created 
in the condenser, the mercury having 
no longer the atmospheric pressure 
to sustain, falls in the tube B, and 
the figures marked on the scale will 
exhibit the extent of the vacuum. 
AYith this arrangement, therefore, there is no necessity 
of making the tube 30 inches in length, as all engines 
are supposed to maintain at least 17 or 18 inches of 
vacuum, and a tube long enough to show this is all 
that is required. Could the surface of the mercury 
remain constantly at A, the divisions on the scale 
would be of equal lengths, and one inch apart, but as 
the mercury rises a little in the reservoir as it falls in the 
tube, the lengths of these divisions vary a little, depend- 
ent upon the relative volumes of the tube and reservoir. 
The aperture in the lower end of the tube is made 
very small, to prevent the oscillation of the mercury. 
At A is a small hole fitted with a screw. This is left 
open, while filling the 



E 


Fi 

ie 

17 
18 
19 
20 
21 
22 
23 
24 
25 
26 
27 
28 




43. 
B 




30 




r. 









i. as an overflow to the 
& so situated that the contents 



g au 8-, 



surplus mercury, it bein 

of the tube B is just sufficient to fill the reservoir to 

the point 30, or the true vacuum line. 

The pressure of the atmosphere, as it varies from 
time to time, does not alter the indications of this 



STEAM AND VACUUM GAUGES. 



11 



gauge, inasmuch as it always exhibits the difference 
between the vacuum in the condenser and a perfect 
vacuum. 

Had the top of the tube B communicated with the 
condenser, and the basin abed been open to the 
atmosphere, the gauge would then have been what is 
termed an open-top vacuum gauge, and would require 
to have been 30 inches in length — the scale being 
reversed, the lowest figure commencing at the bottom. 
With such a gauge, all variation in the pressure of the 
atmosphere affects its indications. 

fig. 44. Figure 44 is a siphon steam gauge, 

filled with mercury to the level a a. 
The short leg connects to the boiler, 
and the long leg is open to the atmo- 
sphere. The steam pressing upon the 
mercury at a, forces up the stick resting 
on the mercury in the other leg at a\ 
showing the pressure in pounds per 
square inch, marked on the scale at the 
top of the gauge. These divisions are 
one inch apart, and indicate pounds 
pressure, for the reason that the descent 



^ 



of one inch in the short leg causes a rise 



inch 



in the long leg, making 



of one 

difference in the level of the mercury 
of two inches, which corresponds to one 
pound pressure ; that is to say, a column 
of mercury two inches high, and having 
a base equal in area to one square inch, 
will weigh in round numbers one pound. 
In making a gauge, it matters not 
what may be the diameter of the tube, 
but whatever it may be, it should be uniform through- 
out, in order that the indications may be correct. 



78 STEAM AND VACUUM GAUGES. 

The stick that is put in the long leg, when there is 
no steam on, has one end resting on the mercury, while 
the other stands at 0. This stick should he made of 
some very light wood — soft white pine answers the 
purpose very well, with the lower end a little the 
largest, in order to have a good bearing on the mer- 
cury. 

To convert this gauge into a vacuum gauge, it 
would be necessary only to connect the long leg to 
the condenser, and attach a scale to the short leg with 
the lowest number commencing at the top. 



CHAPTER IV. 



CASUALTIES, ETC. 



Iloto to act if the Eccentric he broken in an irreparable 

manner. 

If there be two paddle engines connected at an angle 
of 90°, connect the starting bar of the deranged engine, 
by means of a line and guide pulleys, to the cross-tail, 
air-pump beam, air-pump cross-head, or other part 
having motion coincident with the piston of the other 
engine, to give the bar motion in one direction, and 
attach a heavy weight to it, with a line running over 
a pulley, to give it motion in the opposite direction. 

If there be but one engine, connect by similar 
means, to the connecting rod of the deranged engine, 
which will give the proper motion. 

Saw to act when a Steamer springs alealb and com- 
mences to fill rapidly. 

Put am immediately all bilge injections and bilge 
pumps, and shut off all other injections. If they do 
not keep the water down, break the joints on the bot- 
tom or side injections, and allow them to draw water 
from the bilge, taking care to station a man at each 
one to prevent any thing from passing in that would 
choke the valves. 

Vessels are- sometimes* saved from foundering by 



80 

covering the leak with a sail-cloth passed over the 
bows and under the bottom. 

If the leak be a large one, such as one occasioned 
by a collision, it may be possible to force a mattress, or 
something of that nature, into it from the outside. 

How to proceed when all the feed is on and the water 
does not rise in the boilers. 

It sometimes happens that when all the feed is on, 
and the feed pumps are apparently performing their 
usual duty, the water does not rise in the boilers, but 
either retains its level at the time the feed was put on, 
or gradually falls. In this event, one of two things 
must be manifest — either that the water does not enter 
the boiler, or if it does enter, is escaping through some 
other orifice. The first thing, therefore, to do, is to 
examine the check valve to see if it is in operation. 
This can be done by applying the ear to the chamber, 
to ascertain if the valve rises and falls, at each stroke 
of the pump, and also by applying the hand to the 
pipe, immediately below the check valve, in order to 
ascertain if it be cool. If these are found to be all 
right, examine the blow-off cocks, and all other water 
connections with the boilers, to ascertain if they be 
closed ; some of which, in all probability, will be par- 
tially open, but if they should all be found closed, the 
pump must be pumping air into the boilers instead of 
water. The next step would therefore be, to examine 
the pump and induction pipe, in order to ascertain and 
stop the air leak. 

Upon examining the check valve, should it not be 
found in operation, the next step would be to examine 
the pump, to see if it was hot ; also relief and pump 



CASUALTIES, ETC. 81 

valves, to see if they were gagged ; and lastly, the 
eduction pipe, to see if it were burst — either of which 
causes would prevent the pump from delivering water. 
A feed pump may get hot from four causes : 

First. There may be so small a quantity of injec- 
tion water used as to cause it, when delivered to the 
hot well, to be of sufficiently high temperature to heat 
the pump. 

Second. Friction, occasioned from muddy water, or 
tight packing. \ 

Third. The check and delivery valves may be 
caught up or very leaky, allowing the hot water from 
the boiler to run back to the pump. 

Fourth. External application of heat, the pump 
being situated near the boiler or other hot body. 

A feed-pump cannot deliver water when hot, for 
the reason that the vapor constantly generated within 
it, by its elasticity prevents the induction valve from 
opening and admitting water. 

Should the feed pipe burst, it can be repaired tem- 
porarily by wrapping it with canvas coated with white 
lead ; this being secured by strong twine or marline, 
wound closely around the pipe the full length of the 
canvas. 

Should the pipe be split open for a considerable 
distance, it might first be closed with wood or iron 
clamps, as came most convenient, before applying the 
canvas and twine. 

Foaming. 

Foaming, or priming, as it is sometimes termed, is 
violent ebullition or agitation of the water, occasioned 
by an undue relation of temperature between the 
steam and water. Thus, supposing a large quantity 



&2 



of steam to be suddenly taken from the boiler, the 
pressure of steam is immediately reduced below what 
is due to the temperature of the water, and the result 
is a sudden rising up of the water from all parts of the 
boiler. Foam can, therefore, be denned to be a mix- 
ture of steam and water. Boilers are known to be 
foaming when the water does not come out of the 
gauge cocks solid, or when there is a considerable agi- 
tation of the water in the glass gauges. 

To suppress foaming, put on a strong feed and 
blow oft? cut off shorter or partially close the throttle. 
Oil or melted tallow, injected into the boilers through 
the feed pumps, will also prevent foaming, but these 
are somewhat expensive expedients. 

Boilers constructed with insufficient steam room, 
are most likely to foam, because at each stroke of the 
piston a large proportion of the steam is taken from 
the boiler,, and the pressure therefore becomes mate- 
rially reduced. Boilers also constructed in such a 
manner as to prevent the easy escape of steam from 
the surfaces on which it is generated, are likely to 
foam. Thus, supposing there be a large amount of 
heating surface on the crowns and other parts towards 
the bottom of the boiler, and that the steam generated 
on these surfaces in consequence of coming in contact 
with the flues, tubes, braces, &c, can find but a com- 
paratively small exit to the surface of the water, 
the result will be, that where it does escape, it will 
force a large body of water up, mixing it with the 
steam. 

To carry too much water in boilers will cause them 
to foam by reducing the steam room. Running from 
salt to fresh water, or vice versa, will also cause foam- 
ing; in the former case T because fresh water boils at a 



CASUALTIES, ETC. 83 

lower temperature, but a satisfactory explanation of 
the latter case appears to be difficult to arrive at. The 
boilers of sea steamers, when running in muddy rivers, 
usually foam considerably. 

It sometimes occurs, while the boilers are foaming 
badly, that the engines have to be stopped in order to 
take soundings, or from other causes. Now, the first 
thing after stopping the engines, in any case, is always 
to try the water; for it will mostly always be found 
to be lower when the engines are standing still than 
when under way, but when the boilers are foaming, it 
is of the highest importance to try immediately the 
height of the water, for as the foaming ceases after the 
engines are stopped, it may happen that the water has 
fallen entirely out of the gauges and left the lues, in 
which event, if the engines were going to be started 
again in three or four minutes, the better plan would 
be to open the safety valve to keep the water foaming, 
so as to keep the flues covered, and when the engines 
are started again to put all the feed on. But if the 
engines were going to stand still for a considerable 
time, blow off a portion of the steam, if it be too high, 
dampen the fires a little, and put on the auxiliary feed 

The Condenser heats. 

When engines are standing still, it sometimes 
occurs that the condenser gets so hot, that when it 
becomes necessary to start again, the pressure has be- 
come so great in it, that the injection water will not 
enter. Leaky steam and exhaust valves will alone 
cause this, but in no case should it ever be allowed to 
occur. When an engine begins to get hot, the crack- 
ing noise in the condenser, and about the foot valves, 



84 



will always indicate what is going on, time enough to 
check it, which can be done by giving a little injec- 
tion, and causing the engines to make two or three 
revolutions back and forth. If, however, the engine 
should become too hot to take the injection water, the 
only plan will be to blow through, or pump water into 
the condenser if there be such an 'arrangement, or to 
cool the condenser by external application of cold 
water. 

If when under way it is indicated by the gauge 
that the engine is gradually losing its vacuum, apply 
the hand to the condenser, in order to ascertain if it 
be getting hot, and if such be found to be the case 
give a little more injection ; but if that does not help 
the cause, give more still. If the vacuum continues to 
grow less, the probability is that the injection pipe 
has become choked ; in which event shut off that in- 
jection and put on another. Should both the bottom 
and side become choked, inject from the bilge. Should 
the bilge injection also be out of order, the engine will 
have to be stopped, and the snifting valve secured 
down (if there be one) while the injections are blown 
through to clear them. Sea weed, and things of that 
nature, sometimes get over the strainers of injection 
pipes, preventing the entrance of water. 

Most if not all marine engines of modern construc- 
tion are fitted with a thermometer to the hot well, to 
ascertain the temperature of the water, which is usually 
carried from 100° to 115° Fahr. This instrument is 
very important, in order to maintain an even temper- 
ature (the sense of touch of the engineer's hand not 
being delicate enough for that purpose), for it may 
often occur that there may start small leaks about the 
condenser and exhaust pipe joints, which would cause 



; 



CASUALTIES, ETC. 



a decrease in the vacuum, and, as without the ther- 
mometer, the first impulse would be to give more 
injection, with it we would turn our attention to find- 
ing, and stopping the leak. This can be done by hold- 
ing a lighted candle around the joints, and wherever 
there is a leak the flame will be drawn in. To stop it, 
mix a little putty, of white and red lead, and apply it 
to the crevice ; the presence of the atmosphere will 
force it in. 

Getting under way. 

When lying in port, where the steam will not be 
required for at least four or five days, it is proper that 
the water should be blown or pumped out of the 
boilers, and a portion of the man and hand-hole plates 
removed, to allow a circulation of air. When, there- 
fore, the order is given to get up steam, the first thing 
is to see that all these plates are put on, and the joints 
properly made, and this duty should receive the direct 
superintendence of the engineer having charge of the 
same ; for should any one of them leak badly after the 
steam is raised, the departure of the ship might be de- 
layed some hours in consequence. After this duty has 
been properly attended to, open the blow-off cocks and 
run the water up in the boilers to the proper level, or, 
if the boilers are so situated that the water will not run 
up high enough, finish the supply with the hand 
pumps, wood the furnaces while the water is entering 
the boiler, and when the proper height of water is 
attained start the fires. If it be important to raise 
steam quickly, start the fires as soon as water is dis- 
covered in the gauges, continuing the supply while the 
fires are burning. As a small quantity of finely split 
wood, with a little shavings or oily waste placed in 



86 

the mouth of the furnaces, is all that is necessary to 
start the fires, the back part of the furnaces, particu- 
larly in boilers with inferior draft, should be covered 
with a layer of coal to keep out the cold air. 

In raising steam it has been the custom to recom- 
mend that the valves of the engine be blocked open, 
so as to allow the heated air from the boilers to pass 
in and warm up the engine before steam begins to be 
generated ; but as in many cases this is attended with 
considerable trouble, and as the advantages to be de- 
rived from it are very small, it hardly appears to the 
author's mind to " pay." The safety or vacuum valve 
should, however, be kept open until steam begins to 
form, in order to let the heated air escape. The strain 
upon boilers being from the inside, they are con- 
structed and braced with the special view of with- 
standing this strain, many of the braces being entirely 
useless in sustaining a pressure from without ; marine 
boilers are therefore fitted with a small valve opening 
inwards, and weighted so as to open and admit air 
whenever the pressure from within falls to about Hve 
pounds per square inch below the atmosphere. These 
valves are called differently by different parties, as 
follows: vacuum valve, air valve, reverse valve, &c. 

After steam has been raised to 3 or 4 lbs., the 
engine should then be blown through and warmed up, 
and after sufficient steam is raised to move the piston ? 
the engine should be turned over two or three times, 
to see that every thing is right, before reporting 
ready. 

On Coming into Port 

After the engines are no longer needed, before 
hauling the fires, after a long run, it would be well 



CASUALTIES, ETC. 87 

to try the pistons and valves, in order to ascertain 
if - they be leaky. To try the piston, open the water 
valve on one end of the cylinder and the steam 
valve on the opposite end ; if the piston leaks, the 
steam will escape through the water valve. To ascer- 
tain if the steam valves leak, open the water valves on 
both ends of the cylinder. To ascertain if the exhaust 
valves leak, open the steam valves and any cock 
in the exhaust side of the steam chest or exhaust 
pipes. 

While under way it may be discovered that there 
is a slight thump in the engine when passing one or 
or the other or both centres, and the indicator hav- 
ing been applied shows the usual lead, the inference 
is that some part of the working engine is loose ; it is 
important, therefore, to find out what it is on coming 
into port. To do this place the engine on the centre, 
and give the piston steam suddenly by raising and 
lowering the starting bar ; observe closely the cross- 
head, crank-pin, main-shaft, and other main connections, 
to see where the jar is. Should it not be discovered 
after this, jam the cross-head fast, so as to prevent the 
slightest motion, and then give steam as before, in 
which event, if the thump be still felt, the piston will 
doubtless be found to have worked a little loose. 

■ If it be the intention to remain in port several 
days, before hauling the fires, sufficient steam should 
be raised, if the boilers be capable of bearing the 
pressure, to blow all the water out of the boilers. After 
the boilers become cool, the hand-hole plates, over the 
furnaces particularly, should be taken off, to examine 
the crowns, where the greater amount of scale will be 
found deposited, and from which we can judge if the 
boilers require scaling. Mere dampness in boilers is 



88 CASUALTIES, ETC 



found to be injurious, by occasioning a rapid oxida- 
tion, and in order to prevent this, one or two hand- 
hold plates should be taken off the bottom of the 
boilers, in order to let the water drain out dry. It 
would be well also to remove a man-hole plate from 
the top of the boilers to allow a circulation of air. 
If these things cannot be done it will be better to keep 
the boilers filled with water, rather than a small 
quantity in the bottoms. In damp climates, such as 
the Isthmus of Panama, light fires should be made in 
the ash-pits occasionally. 

Scaling Boilers. 

Notwithstanding the water in the boilers is not 
allowed to exceed in density If to 2 per saline hydrom- 
eter, it will be found after a time that a quantity of 
scale, composed principally of lime, has accumulated 
on the crown sheets, tubes or flues, and other parts of 
the boiler. If this be allowed to remain the metal 
will become overheated and burned ; it becomes ne- 
cessary, therefore, to remove it, which can be alone 
done by mechanical means. Sharp-faced " scaling 
hammers" can be used to knock the scale off those 
places that are within the arm's reach, and long bars 
flattened at both ends, and sharpened, called " scaling 
bars," will knock it off the more remote parts. In the 
Martin tubular boiler, which is accessible in every 
part, it is only necessary to condense the steam in the 
boilers for a day or so after the ship comes to anchor ; 
this will soften the scale so that a gang of men may be 
put into them as soon as the man-hole plates are re- 
moved, and scrape off all of it in a few hours. The 
scale, however, must never be allowed to exceed the 
thickness of writing paper. 



COMING TO ANCHOE. 89 

It has been proposed in some quarters to heat the 
tubes or flues by burning shavings, or some other such 
substance in them, and then to cool them off suddenly 
by pumping cold water upon them, the sudden con- 
traction causing the scale to crack off. This plan, how- 
ever, to our mind, does not deserve much favor, and 
never should be resorted to, if the scale can be reached 
in any other manner, for the production of leaks will 
mostly always be the result. 

It is, however, hoped that engineers will soon be 
relieved from this duty, and steamer owners benefited 
by the introduction of fresh water condensers into all 
sea steamers. 

Preparatory to coming to Anchor, or securing to the 

Wharf. 

Fifteen or twenty minutes before coming to anchor, 
or making fast to the wharf, the chief engineer should 
be informed of the fact by the officer of the deck, or 
some other person informed on the matter, so that the 
fires can be allowed to burn down, and the pressure of 
steam permitted to fall to such an extent that the 
necessity for blowing off is avoided. By this means 
the great nuisance of blowing off steam is not only 
obviated, but there is a considerable saving in fuel, 
the fires being permitted to burn down sufficiently low 
to supply only the amount of steam required while 
working the engines by hand, rendering it much easier 
also oil the firemen (whose duties on any occasion are 
arduous enough) by having a very light, instead of a 
very heavy fire to haul. 

In coming to anchor it is usually well to pump a 
little extra water into the boiler, so as to insure a 
proper supply while operating the engines by hand. 



90 THE FIRES WHILE UNDER WAY. 

When it is desired to raise steam, the order from 
the captain should always be what time it is intended 
to get underway, leaving to the discretion of the chief 
engineer to start the fires at such time as he may con- 
sider proper, in order to secure steam and every thing 
ready at the proper time. 

Regarding the Fires while under Way. 

Small as this may appear in the eyes of one not 
practically conversant with the management of the 
steam engine, it is one of the most important things 
that the engineer is called upon to regulate : on the 
one hand, that a proper and uniform supply of steam 
is maintained, and on the other, that more fuel is not 
consumed than is actually necessary to produce the re- 
sult. Different fuels and differently constructed boil- 
ers require the fires to be regulated in a different 
manner, and notwithstanding the repeated efforts, the 
adoption of specific rules, which shall apply alike to 
all, is positively absurd. A few general hints, how- 
ever, touching the leading features, may be useful to 
those who have not had much experience in this mat- 
ter, but they must bear in mind, nevertheless, that 
actual service and observation for themselves, will 
alone make them proficient, no matter how well they 
may understand the chemistry of coal, or the natural 
laws governing the combustion of matter. 

The proper supply of atmospheric air, and the 
proper time for the combustion, are the important ele- 
ments in the consumption of coal. A slow rate of 
combustion, and a moderate draft, always producing a 
better evaporative result, than when the fires are urged, 
occasioning them to be more rapid; and hence, on 



THE FIKES WHILE TJKDEE WAY. 91 

no occasion, should " blowers " be resorted to, if the 
proper supply of steam can be maintained without 
them. 

The fire should be spread uniformly all over the 
grate bars, and in the use of bituminous coal, should 
be from 6 to 8 inches in thickness, but with anthracite 
coal, 4 or 5 inches will be thick enough. So long as 
the ash pit remains bright, there is no necessity for 
slicing or stirring up the fire, but whenever the spaces 
between the bars become choked with clinker, or 
ashes, it will be indicated by the darkness in the ash 
pit, and, if burning bituminous coal, a slice bar should 
be run in through the stoke holes or furnace doors to 
break up the fire and clear out the air spaces. A pick 
applied from below is also very useful in this respect. 
In the use of anthracite coal the pick alone should be 
used ; the breaking up of the surface of such fire, — as 
it does not amalgamate or run together, forming a 
crust like the bituminous, — prevents the regular uni- 
form combustion by allowing too much air to enter 
among the disturbed parts of the coal, it requiring 
considerable time for them again to unite in regular 
ignition after being once disturbed. It is very impor- 
tant that no part of the grate bars be left bare, as the 
admission of cold air, through such space, deadens the 
fire, and cools the flues. It has been ascertained of 
late, that better results are obtained by admitting air 
through a number of small holes in the furnace doors, 
on the plan of W. Wye "Williams, Esq., of England. 

No two furnaces should be fired at the same time ; 
the fresh coal of the one should be fairly ignited before 
a new supply is added to another, in order to keep a 
regular supply of steam. Anthracite coal requires less 
frequent firing than bituminous,, but with either, the 



92 THE FIRES WHILE UNDER WAY. 

coal should not be thrown upon any particular part 
of the furnace, but uniformly all over it. Before 
firing with bituminous coal, it is well to break up the 
upper crust of the fire, which sometimes amalgamates 
so closely as to exclude the proper supply of air. The 
trouble with most firemen is, that they are disposed to 
heap their fires too much, particularly in front, some- 
times half way to the crowns ; this they do for three 
reasons : first, because they suppose the larger the fire 
the greater the supply of steam; second, the more 
coal there is piled in at one time, the less frequent 
they will have to fire ; and third, it requires much less 
labor to shovel the coal into the mouth of the furnace, 
than to supply it uniformly, all over the grates. No 
coal larger than one's fist should be allowed to enter 
the furnace, nor in cleaning the fires, should more than 
one be cleaned at the same time, which should be done 
at stated intervals, unless it so happens, that they all 
or many of them, have got so dirty that a further sup- 
ply of coal is useless, when the engine can be throttled 
off a little while the cleaning is going on. In cleaning 
anthracite fires, care should be taken not to reduce 
them too low, otherwise they will take a long time to 
recover. 

In cleaning fires, as well as when supplying them, 
the furnace doors should not be kept open longer than 
necessary, admitting an undue supply of cold air ; and 
the party, therefore, who, performing his duty as well, 
does it the quickest, is the best fireman. 

The slower a steamer runs the greater distance she 
will perform with the same amount of fuel, provided 
she has not an adverse tide or head winds to contend 
with ; with men-of-war, therefore, it often occurs that 
the saving of fuel is a more important consideration 



PATCHING BOILERS. 93 

than high speed, and for this reason the consumption 
of coal is reduced far below* what would be required 
to keep the vessel up to her maximum speed. This 
can be done in two ways : either by shutting off a por- 
tion of the furnaces entirely, by shutting the ash pit 
doors and closing up the cracks around them with wet 
ashes, or else reducing the quantity of coal consumed 
in each, by covering the back part of the grates with 
a thick layer of ashes. When the diminution in the 
quantity of coal is not very large, this latter plan is 
the better, by retaining the original heating surface at 
the same time that the combustion of coal is allowed 
to go on very slowly, an end very desirable to secure. 
When, however, the reduction in coal is very consid- 
erable, some of the furnaces can be shut off, while the 
back ends of the grates of the remainder can be kept 
covered with ashes. Men-of-war sometimes proceed at 
half or less speed, and as a large extent of boiler sur- 
face occasions considerable loss from radiation, in such 
cases it will be more economical to shut off some of the 
boilers and continue with a moderate supply of fuel in 
the remainder. The furnaces and ash pits of the boil- 
ers shut off should be closed tightly, to prevent cold 
air from passing in to cool the surfaces of the other 
boilers, or to injure the draft. 

After a boiler is shut off, the steam should not be 
allowed to escape, but to remain in it and condense, to 
freshen the water. 

Patching Boilers. 

Inasmuch as all things constructed by human hands 
are liable to decay, steam boilers are not exempt from 
this infallible law ; they therefore frequently require 
to be patched, new stay bolts and braces to be put in, 



94 PATCHING BOILEKS. 

old rivets cut out and replaced with new ones, &c. In 
patching boilers, wherever the defective part can be 
reached so as to work at it well, it is best to cut it out 
and rivet a patch on, calking the seams ; but as this 
cannot always be done, the most common practice is 
to put a patch over the defective part, securing it with 
bolts and nuts, or tap bolts, and making the joint with 
stiff putty, composed of white and red lead, and a 
small quantity of fine iron borings. A piece of sheet 
lead fitted over the place to be patched, will answer 
for the pattern to make the patch by, which, however, 
before the joint is made, should be fitted snugly to its 
place while hot. 

Owing to imperfection in the iron, small cracks are 
sometimes discovered in the flues or other parts of the 
boiler, subject to a high temperature. Should these 
not be more than two or three inches in length, they 
can be stopped by drilling holes and putting in three 
or four small rivets, hammering the heads well down 
so as to cover the crack. 

A leaky stay-bolt, or rivet, has, like the toothache, 
but one sure remedy, and that one is to cut it out and 
put in a new one. 

In cutting out a stay-bolt fitted with a socket, the 
latter can usually be saved and retained in its place, 
ready to receive another bolt ; but sometimes a screw 
bolt is cut out which has to be replaced with a socket 
bolt, and as this may be in such part of the boiler 
which cannot be reached by the arm, or tongs, a very 
good plan to get the socket in its place, is to pass a 
string through both holes and secure the ends, drop- 
ping the centre down and hauling it out through a 
hand hole ; cut the string in two, pass the ends through 
the socket, join them together again, and haul the 



FLUES AND ASH PITS. 95 

socket to its place. In the fitting of sockets, it is very 
important that they should be the exact distance be- 
tween the sheets, with the ends filed square, otherwise 
the sheets will be drawn out of shape. 

Sweeping Flues. 

One of the most disagreeable parts of the duties is 
that of cleaning flues, from the fact of its dirtying 
every thing round about or in the vicinity of the boil- 
ers, the slightest draft being sufficient to waft the light 
dry ashes in every direction. A little water sprinkled 
on them before they are hauled out of the connections 
or smoke-boxes will prevent this in a measure, the 
damper and ash-pit and furnace doors being closed, to 
prevent the men from being suffocated who go inside. 
The lower flues, particularly, are apt to leak a little, 
and the salt water, mixing with the ashes, forms a solid 
mass, which can only be removed by being cut out, 
the flue brush being of no avail. The hammer and 
chisel, and long, sharp-pointed bars, and sledge, are 
best adapted to the purpose. In the use of these 
instruments, care should be taken that they be not 
driven through the metal or under the seams. 

Ash Pits. 

The ash pits should be cleaned out every watch, 
and the ashes thrown overboard, picking out first any 
lumps of coal that may have fallen among the ashes. 
When not running at full speed, a portion of the cin- 
ders may be thrown upon the fires again, after damp- 
ing them with a little water. So also should fine 
bituminous coal be dampened before being supplied 
to the furnaces, the arguments to the contrary not- 
7 



96 STAYS AND GRATE BARS. 

withstanding ; for though it does take a little heat from 
the fire to evaporate the water mixed with the coal, a 
saving is effected, by preventing the coal from being 
drawn — particularly in boilers with strong draft — 
through the flues and lodged in the connections, or out 
of the smoke-pipe. No more water, however, should 
be put on the coal than just sufficient to dampen it. 

Smoke-pipe Stays 

Require to be looked to occasionally, when made 
of rope, as they grow a little slack from time to time. 
These should always be adjusted while the pipe is hot ; 
otherwise, if they be set up while the pipe is cool, the 
expansion after it becomes heated will, in all proba- 
bility, " carry " either the stays themselves away, or 
the band securing them to the pipe. In a gale of 
wind, when the ship is rolling heavily, these stays 
should be looked to, in order to tighten any of them 
that may have become slack, so as to throw the strain 
alike on all. Hemp rope is a very inferior article for 
such purpose as stays for smoke pipes, and we can see 
no good reason, unless it be prejudice, (which is always 
a good reason to those under such influence,) why it 
has been so long retained. Good wire rope looks bet- 
ter, is cheaper, and will last a great deal longer, and 
requires much less attention. 

Grate Bars, &c. 

When fitted new, are usually allowed plenty of 
play, both fore and aft and sideways, to allow for ex- 
pansion after they become heated. The spaces at the 
end of the bars, however, become choked up with 
ashes, which become, by and by, so hard as to form 



BROKEN AIR-PUMP. 97 

almost a solid mass, defeating the objects for which 
they were left. These spaces, therefore, in port, 
should be cleaned out occasionally. 

Ash pits, in port, should also be well cleaned and 
painted, to prevent oxidation. At sea, no water should 
be thrown into them upon the ashes, but they should 
be kept as dry as possible. With these precautions, 
they will last as long as other parts of the boiler. 
Boilers unused for any considerable time should be 
kept dry of water, and have fires made occasionally in 
the ash pits, to evaporate all interior deposit of damp- 
ness — the neglect of this precaution is the sole cause 
of the oxidation and deterioration of all boilers when 
not in use. 



Broken Air-Pump. 

Should the air-pump become broken in an irrepar- 
able manner, and the engine be a single one, there is 
but one thing that can be done, and that is to work 
non-condensing. If there be two engines, we have 
three resorts: to work the broken engine non-conden- 
sing, to disconnect from the crank pin and proceed 
with one engine, or, if there be facilities on board, to 
join the exhaust of both engines with a pipe, and use 
one air-pump and one condenser for both engines. 
This latter plan was tried very successfully for a short 
run on board the U. S. Steam Frigate " Powhatan," 
on the China station, in the summer of 1855. Peculiar 
facilities were, however, offered in this case, as the ex- 
haust side pipe of each engine had a man-hole in it, to 
which the connecting pipe was joined. 

In running under such circumstances, care should 
be taken not to overload the air-pump. 



98 CYLINDER HEAD AND SELECTION OF COAL. 

Broken Cylinder Head. 

Water may be worked over into the cylinder sud- 
denly, from boilers foaming badly, or otherwise, faster 
than it can escape through the water valves, and being 
nearly non-compressible, something must give way, the 
cylinder head, or bottom, being the most likely thing to 
go. In such an event, if there be a spare one on board, 
put it on ; if not, while the old one is being repaired, if it 
be reparable, the following plan can be resorted to ; 
Disconnect the steam and exhaust valves from the 
damaged end of the cylinder, if the engine be fitted 
with poppet valves, and let the atmospheric pressure 
force the piston in one direction, the steam being used 
for the opposite direction. Should the engine be fitted 
with a slide valve, close up the opening into the dam- 
aged end of the cylinder, by fitting in, steam-tight and 
in a substantial manner, a block of soft wood. This 
should not, however, be resorted to, except in cases of 
great emergency. Cylinder heads should have man- 
hole plates of less strength than the heads ; this would 
prevent the destruction of heads in all cases. 

The selection of Coal. 

The kinds and qualities of coals are so varied that 
no general rules can be given for their selection, but 
there is one point, however, which we think will not 
be disputed, and that one is, whenever there is a 
choice-,, the only sure plan is to select the best ; for, 
though its first cost may be a little more, it will prove 
to be the cheapest in the end. "What economy is there 
in purchasing one coal because it can be obtained 10 



SAFETY VALVE. 99 

or 15 per cent, cheaper than another, when there will 
be burned, to produce the same effect, from 20 to 25 
per cent, more than would be burned by the better 
kind ? Yet this is a thing of daily occurrence. But, 
regardless of the money view, there are other disad- 
vantages attending the use of the inferior coal. From 
the fact of there being more burned, the firemen have 
more to supply to the furnaces, and it requires, on 
their part, greater care and attention to keep the fires 
in good order ; thus imposing extra duty on a portion 
of the ship's crew whose energies are usually overtaxed. 
Besides, to convey the vessel a given distance, an extra 
quantity has to be taken on board, which, in the case 
of merchant ships, diminishes their freight capacity, or, 
in war ships, lumbers the deck with a useless number 
of ba^s. 

Some boilers are best adapted to bituminous coals, 
others to anthracite, and the one or the other of these 
coals which should be selected, depends upon the cir- 
cumstances, therefore, for which they are intended. 

In the selection of coals, it is an object, to obtain 
those free as possible from earthy impurities. Slate, 
and such like matter, is to be avoided. Sulphur in 
bituminous coals makes them the more liable to spon- 
taneous combustion. So also receiving them on board 
wet will endanger spontaneous ignition. Coals which 
have been exposed a long while to the rays of the sun, 
particularly in tropical climates, undergo a gradual 
decay, reducing their evaporative qualities. 

Safety Valve. 

Steam, when once commencing to blow off, will 
not cease when the pressure has fallen to the pressure 



100 SAFETY VALVE. 

due to that for which the safety valve is loaded, but 
will continue to blow-off until the pressure has fallen 
some pounds below this. This is owing to the increased 
area which the steam has to act upon when the valv 
is open over what it has when the valve is closed, oc 
casioned by the bevel of the valve face. In a heavj 
sea, the safety valve may be forced open for a shorf 
time, even when the pressure is below that for whicl 
the valve is loaded, by the oscillation of the ship. 



CHAPTER V 



MISCELLANEOUS. 



The Theory of the Paddle Wheel; the Radial compared 
with the Feathering Wheel. 

To all those whose minds have a tendency to probe 
beyond the superficial crust of any thing that may be 
presented to their consideration, the theory of the ac- 
tion of the paddle wheel on the water must be one of 
interest, and any thing, therefore, tending to make 
this subject the more clear, cannot fail to receive the 
proper attention and a careful perusal. 

In regard to the paddle wheel, many theories have 
been advanced, some of them so positively absurd that 
it is difficult for us to conceive how they ever found 
their way into print. Even in reference to the subject 
of centre of pressure of the paddles, such rules as the 
following have been put forth from quarters to which 
we should have looked for more correct information : 

" The circle described by the point whose velocity 
equals the velocity of the ship, is called the rolling cir- 
cle, and the resistance due to the difference of velocity 
of the rolling circle and the centre of pressure is that 
which operates in the propulsion of the vessel.' 1 * * * 

Rule: "From the radius of the wheel subtract the 
radius of the rolling circle, to the remainder add the 
depth of the paddle board, and divide the fourth 



102 THEORY OF THE PADDLE WHEEL. 

power of the sum by four times the depth ; from the 
cube root of the quotient subtract the difference be- 
tween the radii of the wheel and the rolling circle, and 
the remainder will be the distance of the centre of 
pressure from the upper edge of the paddle. The 
diameter of the rolling circle is very easily found, for 
we have only to divide 5280 times the number of miles 
per hour by 60 times the number of strokes per min- 
ute, to get an expression for the circumference of the 
rolling circle, or the following rule may be adopted : 
Divide 88 times the speed of the vessel in statute miles 
per hour, by 3.1416 times the number of strokes per 
minute ; the quotient will be the diameter in feet of 
the rolling circle." 

Now, then, I suppose no one who has given the sub- 
ject the slightest attention would imagine, for one mo- 
ment, that so long as the immersion remained constant, a 
difference in the slip of a common radial wheel would 
make a difference in the centre of pressure of the pad- 
dles ; yet if any one will take the trouble to work out 
the centre of pressure of any wheel by the above rule 
with different slips, he will find the centre of pressure 
continually changing. To suppose such a thing to be true 
would be as absurd as to suppose the centre of pres- 
sure of a plank immersed vertically in a stream moving 
at the rate of 10 miles per hour, to be in a different 
place from what it would be shonld the stream move 
at the rate of 5 miles per hour. 

"We have thought it advisable, therefore, to go into 
this subject the more fully, and give the following as 
an illustration of our views : 

It is generally admitted that the total loss of effect, 
or power, in the common radial wheel, is the sum of 
the losses of the oblique action on the water and the 



THEORY OF THE PADDLE WHEEL. 



103 



slip. The former is calculated by taking the mean of 
the squares of the sines of the angle of incidence at 
which the paddles strike the water, or which is the 
same thing, the means of the squares of the cosines of 
the angles of the arm and water ; for one angle is the 
complement of the other. This will appear plain from 
an inspection of figure 1. A C is the arm, making 



Fig, L 




an angle at C, with the vertical line CA'; A B, the 
breadth of the paddles, and E F, the surface of the 
water. ISTow, it is manifest, that, inasmuch as the ves- 
sel is moving in a horizontal direction, the line B D at 
right angles to that direction, represents the only por- 
tion of the paddle A B that is efficient in propelling 
the vessel, and the line A D represents that portion 
of the paddle that tends to lift the vessel out of the 
water, which, consequently, as it produces no propul- 
sive effect, must be entirely lost. But the line A B, 
being the breadth of the paddle, we will suppose rep- 
resents the pressure it exerts on the water, which, 



104 THEOEY OF THE PADDLE WHEE1 

according to the resolution of forces, is divided into 
two other pressures. A D, tending to lift the vessel, 
is the useless pressure, and B D, at right angles to the 
vessel's path, is the efficient pressure, or the portion 
that is utilized in propelling the vessel. Power, how- 
ever, is not composed of pressure alone, but is com- 
pounded of pressure and velocity, and as the velocities 
of the columns of water, having ADBD for the base 
depend upon the lengths of those lines respectively ; 
that is to say, if we double the length of either one 
of them, say B D, for instance, diminishing the angle 
at C, we not only double the quantity of water dis- 
placed in any given time, but it is also displaced with 
double the velocity ; the power, therefore, developed 
is the product of these two, or as the square. Hence, 
it follows that, since A D represents the useless pres- 
sure, the square of that line must represent the useless 
or lost power ; or, more correctly, the loss of useful 
effect, and the square of B D, the power that is applied 
to propelling the vessel. Now, then, considering A B 
to be unity, the square of B D will be the square of the 
natural sine of the angle BAD, and the square of 
A D the square of the natural sine of the angle A B D ; 
but the triangles A B D, A C D', being similar, the 
angles at B and C are equal, and the loss of effect is, 
therefore, simply represented by the square of the sine 
of the angle that the oblique arm makes with the per- 
pendicular ; but as the angle is continually changing, 
as the arm moves through the water, we have to take 
the mean, and the more numerous, therefore, the divi- 
sions are made, the nearer correct will be the result. 

Thus, supposing, as per figure 2, a wheel 26 feet 
diameter, from outside to outside of paddles, 6 feet- 
immersion of lower edge of paddles, and 20 inches 



THEOEY OF THE PADDLE WHEEL. 



105 



breadth of paddles, the loss from oblique action is 
calculated as follows, the arc being divided into divi- 



Fig. 2. 




sions of 5° each, which are considered sufficiently nu- 
merous for practical purposes : 



106 



THEOEY OF THE PADDLE WHEEL. 





Anglefe 


Sines of the 






of 


Angles of 






Incidence. 
55° 


Incidence. 




* 


.81915 


.33550 = half of the square of sine 




50° 


.76604 


.58681 = square of sine. 




45° 


.70711 


.50000 " 




40° 


.64279 


.41317 _*= " 




35° 


.57358 


.32899 — " 




80° 


.50000 


.25000 = " 




25° 


.42262 


.17860 = 




20° 


.34202 


.11697 = " 




15° 


.25882 


.06698 = " 




10° 


.17365 


.03015 = " 




5° 


.08716 


.00759 = " 




0° 


.00000 


.00000 = " 




5° 


.08716 


.00759 = " 




10° 


.17365 


.03015 = " 




15° 


.25882 


.06698 = " 




20° 


.34202 


.11697 = " 




25° 


.42262 


.17860 = " 




30° 


.50000 


.25000 = " 




35° 


.57358 


.32S99 = " 




40° 


.62279 


.41317 = u 




45° 


.70711 


.50000 = " 




60° 


.76604 


.58681 = " 


if" 


55° 


.81915 


.33550 = half of the square of sine. 


22 


5.62952 



As 22 : 5.62952 : : 100 : 25.588 per cent, of the 
power applied to the wheels. 

Half of the square of the sine at the angle of 55° is 
taken, because the paddle in that position is only half 
immersed, consequently only half the power can be 
expended on it as if entirely immersed ; and the angles 
are put down twice, because the loss is the same after 
the paddle leaves the vertical position as before it 
reaches it. The power in the latter case being ex- 
pended in forcing the water downwards, and in the 
former case in lifting the water, neither of which as- 
sists in propelling the vessel, the only tendency being 
to lift the bow, and depress the stern. 

Slip. 

The loss of effect from slip is usually considered 
the difference between the velocity of the centre of 
pressure of the paddles and the velocity of the vessel. 



THEORY OF THE PADDLE WHEEL. 107 

Thus, if the velocity of the centre of pressure of 
the paddles exceeds the velocity of the vessel by 18 
per cent, of the speed of the paddles, 18 per cent, is 
considered the loss of effect from slip. This we con- 
ceive to be an error. The 18 per cent, is the difference 
between the velocity of the paddles and the velocity 
of the vessel, nothing more; and, therefore, simply 
represents the slip in per cent, of the paddles, but not 
the loss of effect from slip. For it has been shown 
that the loss resulting from the oblique action of the 
paddles on the water, is as the squares of the sines of 
the angles of incidence, and if we suppose the wheel 
to be immersed to its axis, the loss from this cause on 
the paddle, when in the horizontal position — the angle 
being 90° — is 100 per cent., and if the loss from slip 
of 18 per cent, be added to that, we have a total loss 
of 118 per cent., or more than the power applied. A 
positive absurdity. Or, again, supposing the vessel to 
be made fast to the wharf, the difference between the 
velocity of the paddles and the velocity of the vessel 
will be 100 per cent., and as the loss from oblique ac- 
tion cannot, from this circumstance, be any less than 
if the vessel was moving ahead, there will be a total 
loss of the power applied to the wheels of 125.588 per 
cent. A result equally absurd. 

At the angle of 45° it has been seen that only 
.70711 part of the area of the paddle is effective in 
propelling the vessel, and that at this angle the ve- 
locity of the column of water driven aft is only .70711 
of what it is when the whole area of the paddle is 
effective, hence the power expended in slip — .70711 
X. 70711 — 5, the slip in the vertical position being 
considered 1. 

Now, then, if 18 per cent, is the loss from slip 



108 THEORY OF THE PADDLE WHEEL. 

when the paddle is in the vertical position — which 
must be the case if its velocity exceeds that of the 
vessel by 18 per cent, of its own speed — from what 
has just been shown, at the angle of 45°, the loss can- 
not be more than half of 18, or 9 per cent. The same 
reasoning will demonstrate, that at the angle of 30° 
the loss from slip cannot exceed f of 18, or 13.5 per 
cent. Thus we see the loss from slip goes on decreas- 
ing from the vertical to the horizontal position, at 
which place it becomes nothing. We can, therefore, 
approximate very nearly to the true loss in the present 
radial wheel, by taking the mean of these losses at the 
angles as laid down in figure 2. They are as follows: 

At 0° = 18 — .0000 =JL8 per cent. 

u 5° = 18- .1366 =TT8634 " " 

« io° = 18 - .5427 = 17.4573 u " 

" 15° = 18 — 1.2056 = 16.7944 u " 

" 20° = 18 - 2,1055 = 15.8945 " " 

« 25° = 18 - 3.2148 =±= 14.7852 " " 

" 30° i= 18 - 4.5000 = 13.5000 " u 

" 35° = 18 - 5.9218 ±= 12.0782 " " 

« 40° = 18 - 7.4371 = 10.5629 " " 

" 45° = 18 — 9.0000 = 9.0000 " " 

" 50° = 18 - 10.5626 = 7.4374 " " 

" 55° = 18 — 12,078 = 5.9220 " " 
2 138.3343 
2 



Doubled for both sides of the vertical ) _ _ 276 668f> 

18.0000 



294.6686 



294.6686 

— 09 = 13.394 per cent, of the power applied to 

the wheels. 



THEOEY OF THE PADDLE WHEEL. 109 

The same result is obtained as follows : 

100.000 (power applied) — 25.588 (oblique action) 

X 18 per cent, (slip of the vertical paddle) =i 13.394 

per cent. 

We have, therefore, for a total loss in this radial 

wheel, 25.588 + 13.394 = 38.982 per cent, of the power 

applied to it. 

Feathering Wheel, 

Let us take a feathering wheel, of the same di- 
ameter of centre of pressure, i. <?., 26 feet 4 inches in 
diameter from outside to outside of paddles — same 
immersion, breadth, and number of paddles, and see 
how it compares with this. 

It is conceived by some that the only losses in this 
kind of wheel are the friction of the eccentrics, &c, 
and the slip, but there is another loss with deep im- 
mersions, or light slips, occasioned by the drag of the 
paddles as they enter and leave the water. 

In figure 3, the paddles are supposed to be verti- 
cal from the time they enter until they leave the 
water, and the positions of the arms will be seen at 
the degrees there laid down. The perpendicular lines 
drawn across the arcs are intended to represent the 
breadth of the paddles. It is plain that while the axis 
of the paddle moves from A to B, it moves horizon- 
tally the distance A C, and vertically the distance 
C B, and, supposing the vessel to be moving with the 
same velocity as the paddles, it will travel the distance 
A B, while the paddle travels horizontally the distance 
A C. Now, the distance A C being less than A B, 
the paddle in this position cannot be giving out any 
power, but must be keeping the vessel back, by carry- 



110 



THEOKY OF THE PADDLE WHEEL. 



ing a column of water before it, the base of which is 
equal to the area of the paddles, and the length equal 
to the difference in the lengths of the two lines. 



Fig. 3. 




If A B be represented by unity, A C will be rep- 
resented by the natural sine of the angle ABC, and 
if the arc be supposed to be divided into an infinite 



THEOEY OF THE PADDLE WHEEL. Ill 

number of parts, or composed of an infinite number of 
straight lines, A B will be at right angles to A D, and, by 
consequence, the angle ABC will be equal to the angle 
DAE; and as the sine of B represents the distance 
traveled horizontally by the paddle, the sine of D A E 
must manifestly represent the same thing, but the sine 
of D A E is the cosine of D, which therefore repre- 
sents the horizontal velocity of the paddle at the angle 
of 50°, its circular velocity being 1. The difference 
between these two lines is, therefore, the loss from 
drag, supposing there to be no slip, but as all paddle 
wheels must have some slip, when they are propelling 
a vessel, the line A B, diminished by the amount of 
slip, will represent the distance traveled by the vessel, 
and the loss from drag will therefore, instead of being 
the difference between A B and A C, be the difference 
between a fraction of A B and the whole of A C, de- 
pendent upon the amount of slip. If this fraction of 
A B be just equal to A C, the loss from drag in this 
position becomes ; for, though the paddle be giving 
out no power to the vessel, it occasions no resistance 
to the vessel's progress through the water, because it 
is moving horizontally precisely as fast as the vessel 
itself; and if the fraction be less than A C, the resist- 
ance will, of course, be on the after instead of the for- 
ward side of the paddle, and it must, in consequence, 
necessarily be assisting in propelling the vessel. 

Now, then, from the above, it must be evident to 
any one, that so long as the paddle, after it enters the 
water, is moving horizontally at a less rate than the 
vessel, it cannot be giving out any power, but must be 
an actual resistance to the vessel's progress through 
the water. Taking figure 3, and giving the wheel the 
same mean loss from slip as the radial wheel, viz.. 



112 



THEOEY OF THE PADDLE TVHEE 



13.394 per cent., we will ascertain the loss from slip 
at the different angles, there laid down, and attend to 
the drag afterwards, which is merely slip in the oppo- 
site direction, or what might be termed negative slip. 

To give this wheel the same mean loss from slip as 
the radial wheel, it has to have on the arm when in 
the vertical position, or 



**.* CosineB. 

" 5° = .99619 - .73775 


26.225 

= 25.844 


per cent 

u cc 


" 10° = .98481 - .73775 


== 24.706 


u u 


" 15° = .96593 - .73775 


= 22.818 


u a 


" 20° = .93969 - .73775 


= 20.194 


u u 


" 25° = .90631 - .73775 


= 16.856 


u u 


" 30° = .86603 - .73775 


= 12.828 


u a 


" 35° = .81915 - .73775 


= 8.140 


a u 


" 40° = .76604 - .73775 


= 2.829 


u a 


" 45° = 


0.000 


u u 


" 50° = 


0.000 


u u 


u 55° = 


0.000 

134.215 

2 


u a 


Doubled for "both eides of the vertical ) 
position, $ 


268.430 
26.225 





294.655 
22 



294.655 
13.394 per cent, of the power applied to 



the wheel lost by s]ip. 

At the angle of 55° the paddle is .445 part im- 
mersed, but, being so near, we have taken it at a half 
for simplicity, and for like reason have considered the 
paddle at 50° entirely immersed. 

It will be seen from the above, that the paddle, 
from the time it enters the water until after it passes 



THEORY OF THE PADDLE WHEEL. 113 

45°, is traveling horizontally at a less rate than the 
vessel, and the same effect ensues as it rises out of the 
water ; there must, therefore, be a loss from drag or 
negative slip. Let us see what this amounts to. 

Cosines. 

.73775 -.57358 
At 55° = 5 = 8.208 per cent. 

« 50° == .73775 - .64279 = 9.496 " " 
" 45° = .73775 - .70711 = 3.064 " " 



20.768 
2 

Doubled for entering and leaving, 41.536 

41.536 

— ^ — = 1.933 per cent. 

We have, then, for a total loss in this wheel, slip 
(13.394 per cent.) + drag (1.933 per cent.) = 15.327 
per cent, of the power applied to it. 

The total loss in the radial wheel having been 
shown to be 38.982 per cent, (and in the feathering 
wheel 15.327 per cent.), we have 23.655 per cent. 
in favor of the feathering wheel. But of the whole 
power applied to the engines, about 20 per cent, is ex- 
pended in overcoming friction of ditto, friction of load 
on working journals, working air and feed pumps with 
their loads, &c. Consequently, only 80 per cent, 
reaches the wheels, and 23.655 per cent, of 80 per 
cent, equals 18.924 percent, of the total power applied 
to the engines in favor of the feathering wheel. 

To stand off against this, we have the friction of 
the eccentrics, &c. (an amount that, perhaps, can only 
be estimated) extra weight and wear and tear of the 
wheels. 

It will be seen also from the above, that the differ- 
ence between the velocity of the feathering wheel and 



114 CENTRE OF PRESSURE. 

the vessel being 26.235 per cent, of the speed of the 
wheel, and the difference between the velocity of the 
radial wheel and the vessel being 18 per cent, of its 
speed, it follows that, making the same number of 
revolutions, the speeds of the vessels will be as 73.775 
to 82, or as 1.00 to 1.11 ; consequently, the speed of 
the feathering wheel will have to exceed the speed 
of the radial wheel 11 per cent, to give the vessel the 
same, velocity, but this speed of the wheel is as shown — 
consequent upon there being less resistance to the pad- 
dles — attained by an expenditure of 18.924 per cent, 
less power. 

Centre of Pressure. 

The centre of pressure of a rectangular plane im- 
mersed in a fluid, the upper extremity of which is even 
with the surface of the fluid, is \ from the bottom ; 
but, inasmuch as the pressure is as the depth, when its 
upper extremity is below the surface of the fluid, this 
law no longer holds good. To ascertain the centre of 
pressure in such case, " Jamieson on Fluids " gives the 
following practical rule deduced from elaborate math- 
ematical calculations : 

" Divide the difference of the cubes of the extremi- 
ties of the given plane below the surface of the fluid, 
by the difference of their squares, and two-thirds of 
the quotient will give the distance of the centre of 
pressure below the surface, from which subtract the 
depth of the upper extremity, and the remainder will 
show the point in the centre line of the plane in which 
the centre of pressure is situated." 

This rule can be applied directly to the feathering 
wheel, by taking the mean immersion of the paddles 



CENTRE OF PRESSURE. 115 

as they move through the water, and assuming figure 3 
to be of the same diameter from outside to outside of 
paddles, as figure 2, viz : 26 feet, we find the mean 
immersion of the lower edges of the paddles, after their 
upper extremity gets below the surface, to be 

(29.23 -f- 37.84 -f- 45.59 -f 52.44 -f 58.32 -f 63.09 -f 67.02 -f- 69.78 -f- 71.44) 
19 

2+72:=: 55.87 inches, and upper edge 35.87 inches. 
The mean centre of pressure of the paddles in these 

(55 gya g5 g-j-3 \ 
&5.sr—s&.sf t / i — 46,59 ~~ 35 - 87 = 10 ^ 2 

inches from top, or 9.28 inches from bottom, and the 
mean centre of pressure from the time the paddle 
enters until it leaves the water, 

9.28X^(6.62+^^ 
23 

In the radial wheel, however, as the outer ex- 
tremity of the paddle moves more rapidly than the 
inner extremity, and as the resistance is as the square 
of the velocity, the centre of pressure must be consid- 
erably nearer the outer extremity on this account. 
One-third from the bottom, in this case, is, therefore, 
probably, not much out of the truth ; but as a portion 
of the paddle only part of the time is immersed, we 
take the mean of the third of that portion and a third 
of the whole breadth of the paddle during the time it 
is entirely immersed. 

Thus : (!0±3) X^kh(i^)J = 6 . 3Y inches from 
23 

the bottom, showing the centre of pressure under these 

circumstances to be (8.52 — 6.37 == ) 2.15 inches nearer 

the lower edge of the paddle in the radial than it is in 

the feathering wheel. 



116 THE SCEEW PEOPELLEE. 

Practical Remarks on the Foregoing. 

From what lias been shown, it would appear that 
the use of the feathering wheel over the radial wheel, 
from the great saving it effects, would lead to its uni- 
versal adoption ; but, unfortunately, the practical diffi- 
culties are such that its use is confined within very 
narrow limits. The increased weight of the wheel, 
occasioned by the eccentrics, levers, arms, <fcc, required 
to work the paddles, amounting, in some cases, to 
several tons, causing the pillow-block brasses to wear 
away very rapidly, is a sad objection, to say nothing 
of the excessive friction they produce. Besides, the 
pins operating as the axis about which the paddles 
vibrate are found to wear away very rapidly, requiring 
not only to be replaced frequently, but the noise and 
jar occasioned from the wear becomes very objec- 
tionable. The latter objection, however, can be re- 
moved by the use of lignumvitse pin bearings. 

The Screw Propeller. 

The great advantages derivable from the successful 
adaptation of the screw propeller, particularly to ves- 
sels of war, became well understood in its early his- 
tory, and inventive genius set to work thenceforth to 
perfect this important invention ; all kinds of propel- 
lers sprang into use, many of them possessing neither 
the merit of novelty nor usefulness. One, two, three, 
four, five, six-bladed, true screws, expanding pitch and 
no screw at all, are among the number that have been 
tried experimentally and practically since the intro- 
duction of the screw propeller, and, strange as it may 
appear, notwithstanding the large share of attention it 
has received, the theory of the screw propeller is yet not 



THE SCREW PROPELLER. 117 

generally understood ; but, to our mind, this is owing 
to one great cause ; and that is, to the very important 
fact, that those who have undertaken to explain and 
illustrate it, have apparently thought it more impor- 
tant to give the history and accounts of the experi- 
ments — though both very useful in themselves — than 
to explain the leading features and the laws governing 
its action. Besides, a practical engineer does not wish, 
or if he did, has not the time to spare, to examine 
large volumes to find what might be condensed into a 
few pages. We have, therefore, determined to make 
our remarks on this subject brief, and to confine them 
to those points which we think are the more impor- 
tant, allowing the student to build upon them for him- 
self. 

The surface of a screw blade may be supposed to 
be generated by a line revolving around a cylinder, at 
right angles to the axis, at the same time that it moves 
along it, and should the revolving motion be a constant 
ratio to the motion lengthwise, it will be a true screw. 
Should such a screw as this, Fig. 4, be developed upon 
a plane it will form a Fm. *. 

right-angled triangle, in B 
which A B is the pitch, 
A C the circumference 
described by the extrem- 
ity of the blade, and B C 
the line described by any 
point in the periphery 
of the blade by one con- A 
volution of the thread. To make this the more clear, 
suppose the triangle A B C to be wound round a cyl- 
inder, having a circumference equal to A C, and sup 
pose at C we start to trace a line around the cylinder, 



118 THE SCPwEW PKOPELLEE, 

moving alons: it at tlie same time in a constant ratio, 
and that when we have gone all the way around, ar- 
riving over the starting point C, (C and A will be one 
and the same point in the case supposed) we have 
reached the point B, C B will be the line described, 
which is technically termed the directrix, and A B, 
being the distance moved in the direction of the axis, 
will be the pitch. Should the line A B be a curve, 
instead of a straight line, the screw would have an in- 
creasing or expanding pitch, instead of an uniform 
pitch. Figure 5 will illustrate this: Let the curve 
fig. 5, B C be the curve of the blade, 

and the dotted lines B 5, C c 
be tangents drawn to this 
curve, it will be seen that, at 
different points in the curve 
B C, the velocity of rotation 
remaining constant, the ve- 
locity lengthwise of the axis 
A B varies, growing greater 
as we approach B. This is what is termed an expand- 
ing pitch ; that is to say, the pitch at the anterior por- 
tion of the blade, is less than the pitch at the posterior 
portion. The object of such a pitch is this: the ante- 
rior portion of the blade striking upon water at rest, 
encounters the resistance due to a solid body moving 
through water at rest, but this portion of the blade 
puts the water in motion, it being a yielding medium, 
so that when the posterior portion of the blade follows 
it has to act on water in motion, instead of water at 
rest, and in order, therefore, to make the resistance 
due to all parts of the blade alike, the pitch of the pos- 
terior portion of the blade is increased to the extent 
of the motion given to the water by the anterior por- 
tion. 




THE SCREW PEOPELLEE. 119 

To measure the pitch of a screw blade, did it ex- 
tend all the way round the shaft to a full convolution 
of the thread, all we would have to do, would be to 
measure along the line of the shaft from any point in 
the blade to any point directly over it, and the dis- 
tance would be the pitch, or the distance traveled in 
the direction of the axis by one convolution of the 
thread; but since in practice, in order to secure the 
proper resisting area, a full convolution of the thread 
is not required — a very small fraction of it being 
used — it becomes necessary, therefore, to find the pitch 
from this fraction. Taking figure 4, for instance, let 
B b be the length of the blade, measured on the peri- 
phery, and A C the circumference described by the 
extremity of the blade, B b will be the fraction of the 
blade used, and B a the fraction of the pitch. We 
know, therefore, that, starting from B, and traveling 
along the line B &, when we arrive at the point S, we 
have traveled along the axis the distance B Z>, and from 
this we can ascertain what distance will be moved 
along the axis by continuing all the way round until 
we arrive at C, which will be the pitch. Practically, 
we can measure this in two ways : measure the length 
B b of the blade, and also B a, the length in line with 
the axis, we have then two legs of a right-angled tri- 
angle, from which we ascertain the third, a b. Now, 
then, knowing the circumference described by the ex- 
tremity of the blade, Ave derive the following simple 
proportion : 

As a b : the whole circumference : : B a : the whole 
pitch. 

Or we proceed thus: Lay a straight-edge across 
the face of the propeller, at right angles to the axis, 
and a bevel on the periphery of the blade, and look 



120 THE SCREW PROPELLER. 

them out of wind, the angle enclosed by the two legs 
of the bevel will be the angle B b a, which is termed 
the " angle of the propeller ; " and hence, if B b be 
supposed unity, the fraction of the pitch of the one 
blade will be (B a) the natural sine of the angle B b a, 
therefore, knowing the angle B b a, and the length of 
the blade B £, we ascertain the pitch thus : 

As cosine b : whole circumference of propeller : : 
sine b : to whole pitch. 

The pitch can also be determined by construction, 
without any calculation whatever. Thus, supposing 
the line a b represents the whole circumference of the 
propeller, we draw the line B b at the angle to a b as- 
certained from measurement, and erect the perpendic- 
ular a B, which will give the pitch required. 

In a true screw, it matters not whether we take 
the angle at the periphery or any other part of the 
blade ; for, though the angle will be different, increas- 
ing as we approach the centre, the pitch will be the 
same, it only being necessary to know the circumfer- 
ence at the point where we measure the angle. 

Should the blade not be a true screw, but an ex- 
panding pitch, we have to take the angle at two or 
more points, by drawing tangents to the curve, and 
take the mean, for the mean angle of the blade. Thus, 
in figure 5, the mean of the angles B b A and c C A 
will give the mean angle of the blade. 

Some propellers are made to expand from hub to 
periphery, instead of from anterior to posterior portion 
of the blade. 

To ascertain the pitch of such a propeller, take the 
mean of the angles at several points in the blade, and 
proceed as above. In order to ascertain the pitch of 
any propeller, it is always proper to take the angles at 



THE SCREW PROPELLER. 121 

two or more points in the blade, from which we learn 
whether it expands from hub to periphery, whether it 
be true screw, or no screw at all. 

The fraction of the pitch, as we have explained it 
above, is the fraction of the pitch of one blade, but as 
screw propellers usually have two, three, four, six, <fec, 
blades, constituting fractions of a double-threaded, 
treble-threaded, four-threaded, six-threaded, &c, screw, 
the sum of these constitute the fraction of what is 
usually termed the fraction of the pitch of the screw; 
that is to say, if the screw have three blades, and the 
fraction of the pitch of one of those blades be T ] Yy the 
real fraction of the pitch will be 3 times -J-5-, or \ ; 
for it evidently matters not, as far as this is concerned, 
whether the screw be in one, or divided into a dozen 
parts. 

How to lay down a Propeller. 

Knowing the diameter, number of blades, and frac* 
tion of pitch, we intend to use, we proceed thus : 

Taking figure 6, for in- rio. e. 

stance, draw the line A C, 
equal the circumference of 
the extremities of the blades, 
and from A erect the per- 
pendicular A B, equal the 
pitch ; join B C. Now, then, 
supposing we desire the pro- 
peller to have four blades, and the fraction of the pitch 
to be ^-, lay off B a, equal to T V B A, and draw a <?, 
parallel to AC. a c will be the circumference of the 
extremity of one blade viewed as a disc. Then, taking 
figure 7, we describe the circle ahc, equal A C, figure 





122 THE SCREW PEOPELLEE. 

6, and also the smaller circle, equal the circumference 
of the hub of the propeller ; divide the 
larger circle into four equal parts, and, 
from the centres thus obtained lay off 
a d, hi, if, e e, each equal to a c, fig- 
ure 6, and draw lines from each of these 
points to the centre, terminating in the 
hub ; such will be the projection of a four-bladed, true 
screw propeller, viewed from the stern, from which 
the longitudinal elevation can be drawn. The dimen- 
sions of the sections of the blade depend upon the 
diameter of the propeller, the material of which it is 
constructed, and the pressure it has to sustain. . 

Centre of Pressure. 

All solid bodies moving through a fluid harve a cer- 
tain point called the centre of pressure, which is the 
point where the outer and inner pressures just exactly 
balance. In a screw propeller, the radius of the cir- 
cle, which is equal to half the area of the whole circle, 
described by the periphery of the blades, is the centre 
of pressure from centre of motion. Thus, if a propeller 
be 16 feet diameter, the area of the circle described by 
the extremity of the blades =201.06 square feet, and 
the radius of the circle, having an area equal to half 
this, is 5 feet T| inches, consequently the centre of 
pressure in this propeller is 5 feet *l\ inches from the 
centre of shaft. 

The centre of pressure can also be ascertained in 
the following manner : 

1 +4 + 9+16+25+36+49+64 2{ u 
[ 1 1 1 ! 1 1 1 1 = — = 5 feet 8 

1+2 + 3+4+5 + 6 + 7 + 8 36 

inches, nearly as before. 



THE SCREW PROPELLER. 123 

The line per sketch represents the radius of the 
propeller, and is divided into divisions of 1 foot each ; 
the more numerous, of course, the divisions are made, 
the nearer correct will be the result. 

In these calculations, the area of the hub is 
neglected. 

The above rule holds good so long as there is no 
variation in the pitch from hub to periphery ; but 
should the pitch vary in this direction, the velocity of 
the column of water driven aft from different parts of 
the blade will also vary, effecting the centre of pres- 
sure correspondingly. 

Slip. — The slip of a screw propeller is the differ- 
ence between the velocity of the propeller and the 
velocity of the ship. 

Example. — A propeller having 20 feet pitch makes 
70 revolutions per minute, which propels the vessel at 
the rate of 12 knots an hour, required the slip, the sea 
knot containing 6082 J- feet? 

ANSWER. 

20x70 X 60=84000= speed of propeller in ft. per hour. 
6082fxl2=72992= " vessel " 
11008= slip in feet. 

84000 : 11008 : : 100 : 13.1 = slip in per cent, of 
the speed of the propeller. 

Thrust. — A propeller being put in revolution throws 
a column of water off from the blades in line with the 
axis of the propeller, which, as explained above, is the 
slip ; the resistance of this water acting upon the pro- 
peller blades, tends to force the shaft inboard, which 



124 THE SCEEW PEOPELLEPw. 

resistance has to "be sustained by heavy bearings called 
thrust hearings, and the amount of this resisting pres- 
sure is called the thrust In order, in practice, to as- 
certain the extent of the thrust, an instrument called 
the dynamometer is attached to some part of the shaft. 
This- instrument consists of a combination of levers or 
weighing beams, to the final end of which is attached 
a spring balance, or scale, which indicates the pressure 
in pounds; and this pressure being augmented by the 
number of times the levers are multiplied, gives the 
total pressure, or thrust on the shaft. And the total 
thrust being multiplied into the distance moved over 
in a unit of time by the vessel, shows the actual power 
absorbed in propelling the vessel. 

In the application of the dynamometer, care must 
be taken that it receives the entire thrust of the shaft 
before the indication of the scale is noted. 

Did the propeller and steam piston travel through 
the same distance in any given time, and were all the 
power applied to the piston transmitted to the water 
through the propeller, the total pressure upon the 
steam piston and the thrust of the propeller would be 
identical, but since such is never the case, we ascertain 
the theoretical thrust, thus : 

Total effective pressure on piston in lbs. x 2 length of stroke in ft. x No. of revols. per min. 
Pitch of propeller in feet x number of revolutions per minute. 

= Theoretical thrust in lbs. The difference between 
this and the actual thrust, shows the amount lost in 
friction of engines, propeller, and load, overcoming 
resistance to edge of propeller blades, working pumps, 
etc. The loss from slip is independent of this. 



THE SCKEW PKOPELLEPw. 



125 




Strain upon a Screw Propeller-blade. 

We can best illustrate this by an example. 

Given, circumference of centre of pressure of a 3 
bladed propeller, 30.9 feet ; distance from bub to cen- 
tre pressure 41 inches; pitch 22.5 feet; thrust 12700 
pounds : required, the strain upon each blade at the hub. 

SOLUTION. 

Let F G H be the 

development of the he- 
lix on a plane, draw B D 
at right angles to F H, 
and A E at right angles 
to G H. Trigonometri 
cally, we ascertain the 
angles at A and D to be 

each == 37° 9', and at C and B to be each = 52° 5', and 
the lengths of the lines A E, B D, to be relatively as 
1.000 to 1.237. 

Now, inasmuch as the whole thrust can be supposed 
to be concentrated in the centre of pressure of the blade, 
and as the 12 TOO lbs. is in a line with the axis, it follows 
that, if the line A E represents the direction and amount 
of this thrust, the line B D, at right angles to the pro- 
peller blade at the centre of pressure, according to the 
resolution of forces, will represent the resultant of the 
pressures on the blade, or the total pressure tending 
to break it. But inasmuch as there are three blades, 
the pressure will be divided equally among them all ; 
therefore, each has to sustain but a third of this pres- 
sure; hence 

12700 X 1.237 (proportion B D bears to A E) 

' ~~3 

lbs. pressure on each blade at the centre of pressure. 



5236 



126 THE SCKEW PEOPELLEK. 

The pressure at the hub on each blade equals 
5236 lbs. X 41 ins. = 214676 lbs. acting with the 
leverage of one inch. 

Example 2d. — Suppose, in example 1, the breadth 
of the blades at the hub to be 32 inches, and the pro- 
peller to be made of composition, capable of sustaining 
a pressure per square inch of cross-section of 520 lbs., 
acting through the leverage of 1 inch ; required, the 
mean thickness of the blade at the hub ? 

Solution. — The strength of beams is directly as 
their breadths and the squares of their depths, and in- 
versely as their lengths. In the example before us, 
the propeller resolves itself into a simple beam ; we 

have, then, - — — — — — = 12.9 inches = square of the 
' ' 32 X 520 ^ 

thickness, and v 7 12.9 = 3.59 inches in thickness. 

Helicoidal Area. — As has already been shown, the 
development of the helix on a plane is the hypothe- 
nuse of a right-angled triangle, having the pitch of the 
screw for the height; and the circumference, corre- 
sponding to the radii of the helix, for the base. Now, 
as the propeller can be supposed to have an infinite 
number of helices, each one becoming longer and longer 
as we ' approach the periphery, which alter the lengths 
at the same time, of the hypothenuse and base of the 
triangle, we will suppose the propeller to be divided 
into a number of concentric rings, taking the centre 
line of each, for the helix or hypothenuse of the trian- 
gle ; the circumference corresponding to radii of said 
helix for the base, and the pitch for the height, from 
which we have all the elements required for the cal- 
culation. 



THE SCKEW PKOPELLEK. 



127 



To make this the more clear, take the triangle 
B A C ; the lines B 1, B 2, B 3, B 0, represent the 




helices having the corresponding circumferences of 
A 1, A 2, A3, and A 0. Now, then, if these helices 
be the lengths of the rings, or elements for one entire 
convolution of the thread, all we have to do is to mul- 
tiply it by the breadth of the element, which will give 
the area for one convolution ; but as only a fraction 
of a convolution is used in practice, we multiply by 
this fraction, whatever it may be, and the product 
gives the area for the part used. This mode of calcu- 
lation is, of course, only an approximation ; but when- 
ever the blade is divided into a considerable number 
of elements, say 6 inches in breadth each, the result 
obtains sufficiently hear the truth for all practical pur- 
poses. 

The following is a calculation on the screw of the 
U. S. Steam Frigate "Wabash," and which agrees, 
within a very small fraction, of the area as projected 
upon a plane : 



9 



128 



THE SCKEW PROPELLEE. 



Diameter of screw, 11 feet 4 inches ; diameter of 
hub, 2 feet 4 inches. 



Pitch. 


c 
o 

a 

"H 

o 


Circumferences 
corresponding to 
Kadii of Ele- 
ments. 


Lengths of 

Elements for one 

Convolution of 

the Thread. 


® 

O w 

r- P 


o: 5 

-^ 

? <c £ 

§a 


O IE 
CD ~% 

•a o 
® 


2 S 
o 


A 


B 


C 


D 


E 


F 


G 


H 




ft. 


2.B x 3.1416 
ft. 






DxE 

ft. 


ft. 




ft. 


VA s -f-C 2 
ft. 


FxG 
sqr. feet. 


23 


1.5 


9.42 


24.89 


% 


7.11 


.5 


3.555 


u 


2. 


12.56 


26.20 


" 


7.48 




3.74 


(i 


2.5 


15.70 


27.85 


it 


7.96 




3.98 


(i 


3. 


18.84 


29.73 


" 


8.49 




4.245 


" 


3.5 


21.99 


31.82 


(( 


9.09 




4.545 


«< 


4. 


25.13 


34.07 


(( 


9.73 




4.865 


" 


4.5 


28.27 


36.44 


u 


10.41 




5.205 


" 


5. 


31.41 


3S.93 


" 


11.12 




5.56 


41 


5.5 


34.55 


'41.50 


" 


11.86 




5.93 


" 


6. 


37.69 


44.15 


"/it 


12.12 




6.06 


<( 


6.5 


40.84 


46.87 


" 


12.86 




6.43 


" 


7. 


43.98 


49.63 


3 Al 


13.54 




6.77 


y 


7.5 


47.12 


52.43 


<B 


13.78 




6.89 


u 


8. 


50.27 


55.27 


V« 


13.82 




6.91 


" 


8.5 


53.40 


58.14 


7s 


11.63 


" 


5.S15 



* Helicoidal area of one side of both blades = 80.5 square feet. 

Practical Remarks on the Screw Propeller. 

In the application of power to the propulsion of 
the hulls of vessels through water, a portion of the 
effect is lost by the instrument through which it is 
transmitted. In the common radial wheel this loss of 
effect is compounded of two losses, slip, plus oblique 
action ; in the feathering wheel, slip, plus drag, and in 
the screw propeller, slip, plus friction of the propeller 
blades on the water. That instrument, therefore, which, 
possessing no more practical disadvantages than other 

* For the calculations of the friction of a screw surface on the water, see 
Isherwood's calculation on the " San Jacinto," (Journal of the Franklin Insti- 
tute, Third Series, Vol. XXL, p. 349,) or on the " Arrogant," (Appleton's Me- 
chanics' Magazine, Vol. I., p. 156,) from which the form for the above table is 
taken. 



THE SCREW PROPELLER. 129 

instruments, and which has the sum of its losses the 
least, must be the most economical propelling instru- 
ment. The feathering wheel, from what we have 
seen, would present itself very conspicuously to our 
eye as being the best instrument within our knowledge ; 
but, unfortunately, the practical difficulties are such as 
to preclude its universal adoption. The loss from ob- 
lique action in the common radial wheel, particularly 
where the diameter is comparatively small and the dip 
of the paddles considerable, amounts to an important 
percentage of the total power of the engines; and 
since this loss in the screw propeller does not exist, but 
is replaced by one of much smaller magnitude, viz., 
friction of the blades, it follows, that were the slip of 
the two instruments alike, the screw propeller would 
be the more economical. In practice, however, with 
the screw propeller, when contending against head 
winds, or other increased resistance, the slip is increased 
to a very serious extent. In fact, in some cases it has 
occurred, when the engines were going ahead at nearly 
full speed, the vessel stood nearly still. On the other 
hand, however,- when the sails are set to a fair wind, 
the slip of the propeller is materially reduced, while 
the thrust remains unaltered. The increased slip 
when contending with head winds is also experienced 
with paddle wheels, but they are not affected to the 
same extent as the propeller, the increasing or decreas- 
ing the resistance with the latter instrument, not 
making a vast difference in the revolutions of the en- 
gines (as is the case with the paddle wheel) so long as 
the pressure on the piston remains unaltered. 

In the application of the screw propeller, it is well 
to sink it as low as possible in the water, in order that 
the hydrostatic pressure above may be sufficient to 



130 THE SCKEW PKOPELLEE. 

cause the water to flow in solid, even to the centre of 
the propeller, which, therefore, having the proper 
resisting medium, is less liable to excessive slip. This 
will also prevent the centrifugal action — the throwing 
of the water off radially from the centre — which exists 
to a small extent in some very aggravated cases. 

Increasing the helicoidal surface of the screw be- 
yond what is barely sufficient to transmit the power 
given to it, has no other effect than to occasion an 
increased loss by friction, by the increased surface in- 
terposed. The friction of solids on fluids, unlike solids 
on solids, depending upon the extent of rubbing sur- 
face as one of the elements. The object, therefore, to 
be sought after in practice, is to make the sum of the 
loss by slip, plus friction, as little as possible, and this 
sum, manifestly, must depend, to a considerable extent, 
on the amount of helicoidal surface ; but, nevertheless, 
there appears to be no general rules yet devised, from 
theory or practice, which can be used as a reliable 
guide; different engineers making considerable differ- 
ence in the areas of propellers applied to the propulsion 
of the same sized and modeled steamers. 

Negative Slip. — It would certainly appear a very 
strange anomaly, were one on board a vessel, which he 
should discover from the indications of the log was mov- 
ing actually faster through the water than the screw, 
there being no other propelling instrument ; yet such 
has been apparently the case, and there are, perhaps, to 
this day, persons — though we hope they are very 
few — who think that " a screw propeller may drive a 
vessel faster than it is moving itself. There have been 
cases, it is true, where the log has shown that the ves- 
sel was apparently moving faster than the screw, which 



THE SCREW PROPELLER. 131 

alone was the propelling instrument, but that such a 
thing could be true is absolutely absurd, and hence 
attention was turned to discovering the anomaly. It 
is accounted for in two ways. 

When a body having a blunt stern is drawn through 
water at a high velocity, the water, not being able to 
now in from the sides of the body sufficiently rapid to 
fill the vacuity occasioned by its passage, flows in from 
all other directions, and a column of water, therefore, 
necessarily, follows in the wake of such a body. This 
is the case with screw propeller vessels having blunt 
runs, and, by consequence, the propeller, instead of 
acting upon water at rest, acts upon water in motion, 
having the same direction as the vessel. Now, then, 
supposing a propeller, acting upon water at rest, to 
have a slip of 10 per cent., if a column of water follow 
the ship with the velocity of 11 per cent, of the speed 
of the propeller, which still retains its ten per cent, 
slip, the log, as it takes no cognizance of the velocity 
of this water, would show a negative slip of 1 per cent., 
L &, it would show the vessel to be actually moving 1 
per cent, faster than the propeller, when in reality the 
latter would be moving 10 per cent, the faster. 

To j)roduce such a result as this, of course, possesses 
no mechanical or other advantage ; for power must 
have been originally taken from the engines to pro- 
duce the current, which cannot be returned to its full 
extent. It is, therefore, a very important element in 
the design of a screw vessel to make the run very 
sharp — the lines fine— in order that the water may 
flow in solid at once, to fill the vacuity occasioned by 
the vessel's progress, or the propeller's revolutions. 

The other theory in regard to negative slip is this : 
All known bodies yield to pressure, it being only 



132 ALTERING THE PITCH. 

necessary in order to cause the amount of yield to be 
measurable to make the pressure sufficiently great. 
It is hence conceived, that when a screw propeller is 
in motion, the pressure of the water on the blades causes 
them to spring, thereby increasing the pitch; conse- 
quently, in calculating its speed through the water, if 
we use the true pitch, instead of the pitch assumed, 
while it is in motion,' the velocity given to it will be 
too small, and may be less than the velocity of the 
vessel. 

We would, however, remark, that negative slip in 
a screw propeller, unassisted by sails, is more imaginary 
than real, and could only exist under very aggravated 
circumstances, for a screw propeller usually has about 
20 per cent, slip, at least, and to reduce this to nothing, 
even under the conditions set forth above, would be 
rather a perversion of circumstances. 

Altering the Pitch. 

Propellers are sometimes constructed in such a 
manner that the pitch can be altered, from time to 
time, by altering the augle of the blades, which are 
made adjustable in a large spherical hub. Thus, if it 
be desired to increase the pitch, increase the angles by 
turning round the blades ; or if it be desired to de- 
crease the pitch, reverse the operation. Such an ar- 
rangement, however, in practice, must be confined 
within very narrow limits, for, inasmuch as the surface 
of a screw propeller blade, being that of a helicoicl, 
every point in the blade must have a different angle, 
which increases as the hub is approached, and if the 
propeller be constructed so that all the angles be 
adapted to one particular pitch, it is not very likely 



PARALLEL MOTION". 133 

that they will, after being distorted, be adapted to any- 
other pitch ; that is to say, if the propeller be a true 
screw, for instance, and have a certain angle at the 
periphery, if we move the blade so as to increase the 
angle at that point 10°, the angle at every other point 
in the blade will also be increased 10°, which should 
not be the case, but should be correspondingly less as 
the hub is approached; thus, by this arrangement, we 
give a greater pitch at the hub than there is at the 
periphery ; and if the operation be reversed, and we 
decrease the angle at the periphery, the angle at the 
hub, and every other point in the blade, is decreased 
to precisely the same extent, thus giving less pitch at 
the hub than there is at the periphery, or any other 
point in the blade. We therefore arrive at this con- 
clusion : 

That having three conditions presented to us, viz., 
true screw, expanding screw, from periphery to hub, 
and expanding from hub to periphery — the latter two 
not in regular ratio — it is more than probable that 
one or the other of these must be found practically to 
be the superior, and whichever it may be, and that 
one adopted, the advantage to be derived from alter- 
ing it, after it is once adopted, does not appear very 
plain, the arguments to the contrary notwithstanding. 



Parallel Motion, 

Parallel motion is a combination of bars and rods, 
having for its object the guiding of the piston-rod of a 
steam-engine in a constant straight line, or as near a 
straight line as can be practically attained. It is ap- 
plicable, in different forms, to any type of engine, but 



134 



PAKALLEL MOTION. 



its adaptation to the side-lever engine is the more 
general. 

We have constructed figure 10 with the view of 



Fig. 10. 




illustrating its application to this type of engine, and 
to clear it, if possible, of the mystery that usually 
hangs over it in the shape of formulas. A B is half 
the length of the side lever, vibrating on the centre B ; 
A C, the side rod attached to the cross-head at C ; 
G F, the parallel motion side rod ; D F, the parallel 
bar, and E F, the radius bar vibrating on the. centre E. 
The object to be attained is to make the point C 
travel vertically in a straight line, or as near so as pos- 
sible ; and from the construction of the figure, it will 
be seen that, when the point G moves to the right the 
point F moves to the left, and vice versa ; hence it is 
manifest, that there must be some point H, in the rod 
F G, which will describe very nearly a straight line, 
and if the lengths G B and E F were equal, that point 
would be in the centre of F G ; but, since they are of 
unequal lengths, H must be in such a position that 
EFxFH=rBGxGH. 



PARALLEL MOTION. 135 

Now, then, having secured the point H, draw the 
line B C through H, which will determine C, the cen- 
tre of the cross-head ; and the triangles BHG,BCA, 
being similar, and joined together in such manner that, 
no matter how much the angles of the one may alter, 
the angles of the other must alter to precisely the 
same extent; and hence, these triangles always remain- 
ing similar, it follows that if the apex (H) of the one 
moves in a straight line, the apex (C) of the other 
must move in a straight line also. 

It matters not where the points DFG may be 
situated, so long as D does not coincide with C, and 
the figure A D F G is a parallelogram ; nor does it 
matter about the respective lengths of the sides of the 
parallelogram, so long asEFxFH = B6xGH. 

In practice, it happens sometimes that the parallel 
motion gets out of adjustment, the piston rod perhaps 
rubbing hard on one side of the stuffing-box at the top 
of the stroke, and hard on the opposite side on the 
bottom of the stroke ; or it may rub hard on the stuff- 
ing-box at one end of the stroke, and be quite free at 
the other. Such a result can be brought about in 
three ways only : either the sides of the parallelogram 
ADF6 have got out of parallelism, the radius bar 
E F, of incorrect length from the wear of the brasses, 
&c, or the centre E has by some means been moved 
from its true position. 

These can be all remedied by interposing liners 
at the proper places ; of course, taking care about 
the centre A, in order not to endanger striking 
the cylinder-head, by interposing too much at that 
point. 



136 STRENGTH OF MATERIALS. 



Strength of Materials. 

This is a subject which does not properly come 
within the province of the present Notes; but we 
have, however, thought it well to devote a short space 
to it at this place, confining ourselves to a few practi- 
cal examples. 

Beams. — The strength of beams are to each other 
directly as their breadths and square of their depths, 
and inversely as their lengths. 

Example. — The depth of the beam of an engine 
75 ins. diameter of cylinder, and 7 ft. stroke, at centre 
is 42 ins., and using this as a standard, required the 
depth of one for an engine of 80 ins. diameter of cyl- 
inder, and 8 ft. stroke, the breadth, and also the maxi- 
mum pressure on the steam piston to remain the same ? 

Answer.— 75 2 x 7 : 80 2 X 8 : : 42 2 : 2293.76 ins. = 
square of the depth ; the square root of which, 47.9 
ins., is the depth required. 

These figures, of course, do not apply to the truss, 
but to the solid parabolic beam. 

Shafts. — The strength of shafts to resist a trans- 
verse, or torsional strain, are to each other as the 
squares of their diameters ; for the reason that, if the 
diameter of a shaft be doubled, the quantity of metal is 
increased fourfold, which would occasion the strength 
to increase as the square, but at the same time there 
being double the leverage interposed in consequence 
of the double diameter, which, being multiplied by 
the square (or 4), will give the cube (or 8). 



STRENGTH OF MATERIALS. 137 

Example. — The shaft of a steamer is 1Y inches 
diameter; cylinder, 75 inches diameter; by 1 feet 
stroke ; required the diameter of a shaft for a steamer, 
having an engine of 80 inches diameter of cylinder, by 
8 ft. stroke, taking the shaft here given as the standard, 
the maximum pressure on both steam pistons to be 
alike. 

Answer.— 75 2 x 7 : 80 2 X 8 : : 17 3 : 6388.459, the 
cube of the diameter, the cube root of which, 18.55 
inches, is the required diameter of the shaft. 

This is about the diameter of the shafts used in 
practice for two engines of 80 inches diameter of cyl- 
inder, and 8 feet stroke each. The proportion in prac- 
tice for a shaft for a single engine of this size, is about 
15.5 ins. diameter, which is a little more than half the 
strength of the above shaft, owing to the weight of the 
wheels, <fcc, (which have also to be sustained by the 
shaft) being more than half. 

Screw Propeller Shaft. — The strain on the shaft of 
a screw propeller is of two kinds— one in line with the 
axis tending to compress, the other at right angles to 
the axis tending to twist it. And, inasmuch as the 
strength of a shaft to resist compression, is much 
greater than that to resist torsion, we need only take 
the latter strain into consideration. 

Hence, to ascertain the diameter of a screw shaft, 
the dimensions of the propeller and thrust being given, 
let A B, figure 11, be the pitch, B C, the circumference 
at centre of pressure, and A C, the helix for one con- 
volution at centre of pressure. Draw B D at right 
angles to A C, and D E at right angles to B C ; the 
lines D E and B E will be proportionally the com- 
pressional and torsional strains on the shaft ; hence, if 



138 STEENGTH OF MATEKIALS. 

B E be multiplied by the thrust in pounds, and divid- 
ed by D E, the quotient will be the pressure in lbs., 
fig. it acting at the centre of pressure 

of the blade to twist the shaft. 
This pressure being multiplied in- 
to the leverage of the centre 
v of pressure, and divided by the 

\^ standard of the metal used, will 

x give the cube of the shaft's diame- 
ter, the cube root of which will 
be the diameter. But since the triangles A C B, 
BDE, are similar, from the construction of the figure, 
the angles being respectively equal, the sides must be 
proportional, viz. : A C to B D, A B to B E, and B C 
to D E. Therefore, having the lengths of the two 
sides A B, B C, of the triangle A B C, we have 

V AB~xT^ B C x b ,. , , , , f • • , 

== diameter 01 shaft in inches, 

c 

in which AB = pitch in feet, 

BC = circumference at centre of pressure in 

feet, 

t = thrust in pounds, 

b == distance from centre of shaft to centre 

of pressure in feet, 

c = practical coefficient of the metal used 

for the shaft, per sq. inch of section 

for a leverage of one foot. 

Paddle Shafts. — Example 1. — Area of the piston 
3848.4 sq. ins. ; maximum pressure persq. inch 40 lbs. ; 
stroke 10 feet; one engine; required the diameter of 
the paddle shaft, the practical value of the metal being 
200 lbs. per sq. inch of cross-section,-with a leverage 
of 1 foot. 



STRENGTH OF MATERIALS. 139 



. v/ 3848.4 X 40 X 5 _ 5 . ,. , 
Answer. — — = 15f ins. diameter. 

Example 2. — Same as Example 1, excepting there 
are two engines instead of one, connected at right 
angles ? 

Answer. — With two engines connected at 90°, the 
position in which the greatest pressure on the shaft 
will "be interposed will be when both engines are in 
such a position that a perpendicular, let fall from the 
centre of the crank upon the centre line passing 
through the centre of the shaft, will enclose an angle 
of 45°, which, with a 5 feet crank, will give a leverage 
of 5 x .70711 (nat. sin. of 45°) = 3.535 feet; hence, 
supposing the pressure at this position of the engines 
to be 40 lbs. per square inch, we have 



s/ 3848.4 X40X 3.535 . _„ . ,. , 

X 2 = 17.6 ms. diameter. 



200 



Piston Pods. — The piston rod of a reciprocating 
steam-engine is subject alternately to a tensile and 
compressing strain ; and there is nothing more absurd 
than the rules given in books on the steam-engine, de- 
fining its diameter to be a certain fraction of the diam- 
eter of the cylinder, independent of all other elements. 
For instance, suppose a rod of a certain diameter and 
length to be just able to sustain a certain weight 
placed upon the top of it, without deflexion ; it is ab- 
surd to suppose that it would sustain the same weight 
if the rod was made double the length, retaining the 
same diameter ; yet the rules given for the diameters 
of piston rods are regardless, not only of their lengths, 
but also of the pressure of steam. We have, therefore, 



140 STRENGTH OF MATERIALS. 

thought it well to copy the following remarks and ta- 
ble from Johnson's translations of the book of Indus- 
trial design, by M. Armengaud, the elder, and M. M. 
Armengaud, the younger: 

" Compression is a force which strives to crush, or 
render more dense, the fibres or molecules, of any sub- 
stance which is submitted to its action. 

" According to Rondelet's experiments, a prism of 
oak, of such dimensions that its length or height is not 
greater than seven times the least dimensions of its 
transverse section, will be crushed by a weight of from 
385 to 462 kilogrammes to the square centimetre of 
transverse section, or a weight of from 5470 to 6547 
per square inch of transverse section. 

" In general, with oak or cast iron, flexure begins 
to take place in a piece submitted to a crushing force, 
as soon as the length or height reaches ten times the 
least dimension of the transverse section. Up to this 
point the resistance to compression is pretty regular. 

" Wrought iron begins to be compressed under a 
weight of 4900 kilog. per square centimetre, or of 
nearly 70000 lbs. per square inch, and bends pre- 
viously to crushing, as soon as the length or height of 
the piece exceeds three times the least dimension of 
the transverse section." 

We show, in the following table, to what extent 
per square inch we may safely load bodies of various 
substances : 



SUEFACE CONDENSERS. 



141 



Table of the Weights which Solids — such as Columns. Pilas- 
ters, Supports — will Maintain without being Crushed. 



WOODS AND METALS. 



Description of Material, 


Proportion of Length to Least Dimensions. 


Up to 12. 


Above 12. 


Above 24. 


Above 48. 


Above 60. 


Sound Oak 


lbs. 

426.750 

270.275 

533.437 

137.982 

14225.000 

28450.000 

11707.175 


lbs. 
355.625 
119.490 
440.975 
116.645 
11877.875 
23755.750 


lbs. 

213.375 

71.125 

266.007 

69.709 

7112.500 

14225.000 


lbs. 
71.125 

106.687 

2375.575 
4741.666 


lbs. 
35.562 






Pitch Pine 








Wrought Iron 


1994.900 




2375.575 


Rolled Copper 









Example. — What is the least diameter of a piston 
rod for a cylinder having a cross-section of 3848.4 
square inches, to sustain with safety a pressure per 
square inch of piston of 40 lbs., the proportion of 
length to be about 24 to 1 ? 

Answer. — Taking one half the number in the 
above table for the practical value, we have 

3848.4 X 40 * 

frTl 9 5 9 ~ 43.28604 sq. ins. cross section of the rod, 



, ./43.28604 H , . v x v.. xl , 
and y — — — - — = 7.4 ins. diameter of the rod. 
.7854 



Surface Condensers. 

A surface condenser is an instrument for condens- 
ing steam by contact with cold metallic surfaces, in- 
stead of bringing it directly into contact with a shower 
of cold water. The object of using such a condenser in 
lieu of the common jet, is to furnish boilers of marine 
steamers with distilled instead of sea water, conse- 



142 SURFACE CONDENSERS. 

quently to provide against the loss of fuel otherwise 
occasioned by blowing off a portion of the water, to 
keep the concentration at a desired point, as shown at 
pages 66 and 67. Also to prevent the loss due to the 
little conducting power of the envelope of scale which 
attaches to all heating surfaces of boilers using sea 
water. 

By the use of such an instrument there is also 
gained the saving in labor of scaling and cleaning the 
boilers, which belongs to all sea steamers using the 
common jet, and this is of no small importance to 
those having the care of steam machinery. 

Again, by its use the expense of repairs to the 
boilers is considerably reduced, their durability greatly 
increased, the pressure of steam which can be ju- 
diciously carried is unlimited, and the expansion of the 
steam can be carried to a greater extent. 

With these many marked advantages, it seems ex- 
traordinary that the introduction of surface condensers 
should have met with so little encouragement ; the 
slow progress made has not been owing to any want 
of engineering ability, but solely for the want of pat- 
ronage ; for engineers of talent both here and in 
Europe have devoted their time to the subject for 
many years, and have produced many forms, some of 
which have been so successful as to render, in our 
opinion, the use of jet condensers absurd. Of the 
number invented and introduced into practice, the one 
known as Pirsson's has thus far met with the most 
favor. It is termed a double vacuum condenser, i. e., 
it has a vacuum within and without the condensing 
tubes. The injection water is received upon a scatter- 
ing plate, and showered down on the tubes, which 
condenses the steam within them; this injection water 



SUKFACE CONDENSERS. 143 

with the air and uncondensed vapor is extracted by 
an air-pump, in the same manner as when the jet con- 
denser is used, and the water of condensation is drawn 
away by a separate pump, called the fresh water pump, 
and discharged into a reservoir, whence it is delivered 
by the feed-pumps into the boilers. 

Another variety of condenser, known as Sewell's, 
has recently attracted considerable notice. It has been 
highly reported upon by a Board of naval engineers 
appointed by the Hon. Secretary of the Navy, and has 
been introduced into some of the most successful 
steamers. It is of the close surface type, that is, it has 
a vacuum upon only one side of the condensing tubes, 
the condensation being effected by currents of cold 
water driven through the tubes by a pump. The joints 
of the tubes are made with india-rubber sleeves, so that 
they give perfect tightness, and allow each tube to ex- 
pand or contract by itself, independent of the others, 
and each or all of them can be taken out for cleaning 
or repairs. The vacuum produced by this condenser 
is unequalled, and as there is but one air-pump, it is 
obtained with less power than by the other method. 

Close tube surface condensers had been made with 
the tubes secured at both ends without any provision 
for expansion or contraction, except the buckling of 
the tubes when hot, and stretching when cold. They 
have also been made with one end of the tubes only 
secured, the other ends being fitted to an expansion 
plate. The advantages of Mr.. Sewell's over the latter 
named plans are manifest. 

The following figure* will give the student a clearer 
idea of the construction and operation of Pirsson's 
condenser. A A, is the condenser, in which there is a 

* Taken from "Steam for the Million" by Commands* Ward, U. S. N. 

10 



144 



SURFACE CONDENSEPwS. 



series of small tubes : p, the air-pump ; f, fresh water- 
pump ; £, the exhaust pipe ; ?, the injection pipe. The 




operation is as follows: — The engine being put in mo- 
tion, the exhaust steam flows through the exhaust pipe 
£, into the chambers c c, thence in direction of the ar- 
rows through the tubes to the lower chamber d, injec- 
tion water being: admitted at the same time from the 
sea through the injection pipe Z, is showered by the 
scattering plate m over the tubes, and by its gravity- 
takes the direction of the arrows to the channel way n, 
from which it is removed by the air-pump p y and de- 
livered into the hot well q to the delivery pipe r and 
overboard. 

The water resulting from condensation is drawn 
by the fresh water pump/ from the chamber d, through 
the pipe e e y and delivered into the fresh water reser- 
voir g ; from this reservoir it passes to the feed pump 
i, through the pipe A, and is delivered into the boilers 
through the pipe h. The pipe s is for the purpose of 
supplying salt water when deficiencies occur. 

In this condenser, as drawn, all the tubes are firmly 
secured to both tube heads, but one end of the tube 
box is free, so that all the tubes can expand and con- 



CYLINDRICAL BOILERS. 145 

tract together ; those recently constructed have each 
tube secured to the tube head at one head only, the 
other ends being fitted so that they just pass through 
the holes, thus allowing each tube to expand or con- 
tract regardless of the others. There is also a com- 
munication from the exterior to the interior side of the 
tubes, so that the vacuum within created by the fresh 
water pump is equal to that without, created by the 
large air-pump. In close tube surface condensers, the 
position of the steam and water, as shown in the figure, 
is reversed. The exhaust steam is received on the ex- 
terior of the tubes as at £, and is condensed by water 
entering at <f c, and driven through thetubes by a cir- 
culating pump, attached at b ; it is then discharged 
through a pipe from d. The pump p is converted into 
a fresh water air-pump, receiving the fresh water 
through the channel-way n and foot-valve 6>, and dis- 
charging it into the reservoir y, whence it is received 
by the feed-pump and pumped into the boilers. 



Cylindrical Boilers. 

The force tending to rupture a cylinder along the 

curved sides depends upon the diameter of the cylinder 

fig. 12. and pressure of steam, and we 

©may regard, hence, the total 
pressure sustained by the sides 
to be equal to the diameter x 
pressure per unit of surface x 
length of boiler, neglecting any 
support derivable from the heads, 
w T hich, in practice, depends on 
the length. The shorter the 
tube, the greater its powers of resistance. This is in 



146 CYLINDKICAL BOILERS. 

consequence of the ends being rigid and unyielding. — 
See latest experiments on this subject by William Fair- 
bairn, Esq., C. E., F. E. S. 

The force tending to rupture a boiler is termed, by 
Professor Johnson, the divellant force, and the tenacity 
or strength of the metal which resists the divellant 
force is termed the quiescent force. When rupture is 
about to take place, these two forces must be exactly 
equal. 

Example. — What pressure will a cylinder boiler, 
12 ins. diameter, and J in thickness of metal, sustain 
per square inch, the iron to be of the best English 
iron ? 

The experiments of the Franklin Institute give for 
the strength of single riveted seams, 56 per cent, of 
the sheet, and assuming the tensile strength of the best 
English iron to be 60,000 lbs. per square inch of sec- 
tion, we have 

60,000 x .56 —7001b 

12 (diameter) x 4 (length of band to make 1 sq. in. area of cross section) ' * 

But as the opposite side of the boiler will support an 
equal amount, the true pressure will be double this, or 
1400 lbs. per square inch, one-fourth of which only 
(350 lbs.) would be safe to subject it to in practice. 

From this we see that the bursting pressure of a 
boiler of the dimensions above given, in a transverse 
direction, is 1400 lbs. per square inch. We will now 
see what force this 1400 lbs. exerts to tear the boiler 
asunder in a longitudinal direction. To do this, we 
have only to multiply the area of the head by the 
pressure per square inch, and divide by J the circum- 
ference, (since the iron is | inch thick,) which will 
give the strain upon each square inch of sectional area. 



CYLINDRICAL BOILERS. 147 

rp, 113.09X1400 t. caa1 , • -. 

Thus — - — = 16800 lbs. per square inch 

of sectional area, in a longitudinal direction, and 

1400x12x4 OQflAnl , . , , 
= 33600 lbs. per square inch of sec- 
tional area in a transverse direction. 

The 4 in the latter case is the length of the band 
to give one inch square of sectional area, and we divide 
by 2 because there are two sides of the boiler to sup- 
port the pressure. 

From these figures, it is observed that the strain 
upon a cylindrical boiler, or other cylindrical vessels, 
subject to internal pressure, transversely, is exactly 
double what it is longitudinally. In cast iron, or other 
cast metal cylindrical vessels, this is made amends for, 
in a certain degree, by casting ribs, or bands, around 
the external surface ; but with boilers there appears to 
have been no attempt to increase the strength by riv- 
eting bands at intervals on the outer surface, though 
we see no good reason why such a thing could not be 
done very advantageously. 

"We remark, from what has appeared, that the 
strain upon cylindrical boilers increases transversely 
directly as the diameters, and longitudinally as the 
squares of the diameters — because the areas of the 
heads increase in that ratio — but the circumferences 
increase also as the diameters ; and hence, though we 
obtain four times the pressure longitudinally by doub- 
ling the diameter, we have double the metal in the 
circumference of the boiler to sustain it, and, therefore, 
the strain upon a unit of metal, in this direction, in- 
creases also as the diameter. Hence, no matter what 
may be the diameter of a boiler, the transverse pres- 
sure tending to tear it asunder, will always be double 
the longitudinal pressure. 



148 BOILER EXPLOSIONS. 

Boiler Explosions, 

There is only one grand direct cause of boiler ex- 
plosions, and that is the incapacity of the metal, at the 
time, to sustain the pressure to which it is subjected. 
This can be brought about in several ways ; defective 
material of which the boiler is constructed, defective 
construction, all parts of the boiler being incapable of 
sustaining the same pressure, gradual accumulated pres- 
sure without the means of escape, sudden accumulated 
pressure occasioned by pumping water on red-hot sheets, 
collapse occasioned by a vacuum in the boiler, the re- 
verse valve being inoperative ; collapse of flue occa- 
sioned by internal pressure in the boiler and a partial 
vacuum in the flue; overheating the plates, brought 
about by the accumulation of large quantities of scale 
upon them, thereby reducing their tenacity. 

Boilers having been previously tested by hydros- 
tatic pressure considerably beyond the limit to which 
it is intended ever to allow the steam to reach, and 
each and every boiler being fitted with steam and wa- 
ter-gauges, proper sized safety-valves and such like in- 
struments, there is never any good excuse, under any 
circumstances, for the cause of boiler explosions. In- 
competency or recklessness must be somewhere mani- 
fest, for the engineer, knowing the pressure which his 
boiler will with safety bear, should under no circum- 
stances allow it to exceed that pressure. "We would, 
however, observe here, that we have noticed in many 
cases, both ashore and afloat where there are a number 
of boilers connected together, instead of having a 
steam gauge attached to each one separately, there was 
but one gauge to the whole number ; and hence, if one 
or more boilers be shut off from the others, there would 



BOILER EXPLOSIONS. 149 

be no means of ascertaining the pressnre within them ; 
and it is a very common thing with land boilers and 
boilers of small river boats to have no steam-gauge 
-whatever. In such cases as these the owners take 
upon themselves the responsibility, which would other- 
wise be attached to the engineer, of any disastrous 
result. 

The legislation in regard to the inspection of steam- 
boilers is hardly adequate to the cause ; for though the 
testing the strengths of boilers, from time to time, is 
very good as far as it goes, it falls short of what the 
seriousness of the case demands. The same amount of 
strict, unbiased inspection on the parties who have 
charge of the very powerful, yet governable element 
of steam, would be followed by far more beneficial 
results. Place only those in charge of the steam- 
engine, boilers, and dependencies, who are competent 
to the task ; prevent owners from employing any one 
simply because his services can be secured for a small 
compensation, and then you touch the subject in a vital 
point. It is too prevalent an opinion, that any one 
who can stop and start an engine, have the fires started 
and hauled, is an engineer, regardless of his knowledge 
of the element of which he has charge. 

It is true, however, that the system of rivalry and 
competition, carried on by steamboat owners and others 
using steam power, is such as to prevent any one inde- 
pendently from paying a very high rate of compensa- 
tion; but if all were compelled to employ equally 
competent services, no difficulty could be experienced 
on this head. 



150 HORSE POWER. 



Horse Power 



The standard for a horse power in England and the 
United States is pretty generally established at 33000 
lbs. raised one foot high in a minute ; but in France a 
horse power is estimated at 75 kilogrammetres, which is 
75 kilogrammetres raised one metre high per second, 
equal to 32554.7 lbs. avoirdupois, raised one foot high 
per minute. To ascertain the horse power of a steam 
engine, multiply the mean unbalanced pressure per 
square inch on the piston, by the area of the piston in 
square inches, by the length of the stroke in feet, and 
by the number of strokes in a minute; and divide by 
33,000, the quotient will be the horse potver. 

From this figure, in order to ascertain the actual 
power utilized in propelling the vessel, a deduction has 
to be made for working the air and feed pumps with 
their load, friction of working journals, friction of load 
on working journals, amounting in all to about 20 per 
cent, of the total power, leaving 80 per cent, to be ap- 
plied to the propelling instrument, which 80 per cent, 
has to be reduced by the amount of loss which obtains 
in the propelling instrument. 

Example. — Eequired the horse power of a con- 
densing steam-engine, having a cylinder 70 inches 
diameter, by 10 feet stroke, making 15 revolutions per 
minute ; mean pressure of steam throughout the stroke 
23 lbs. ; back pressure 3 lbs. ; and also the actual 
power utilized in propelling the hull of the vessel, the 
sum of losses in the propelling instrument being 40 
per cent, of the power applied to it ? 

Answer 1st. — 
70 2 X.7854x 23-3x10x15x2 ... h , 
33000 ~ e P ower - 



HOESE POWER. 151 

Answer 2b. — Considering 20 per cent, of the total 
power to be expended in working pumps, in friction, 
<fec, we have 80 per cent, applied to the propelling 
instrument, and 40 per cent, of 80 per cent. = 32 per 
cent, of the total power expended in transmission 
through the propelling instrument ; wherefore, 80 — 
32 = 48 per cent, of the total power applied to pro- 
pelling the hull of the vessel = 335.856 horses. 

Nominal Horse Power, is a term which expresses 
neither the actual power, the size of the engine, nor 
any thing else which is useful ; and though it has be- 
come almost obsolete among well-informed engineers 
in this country, our trans-atlantic friends seem yet to 
cling to it with some tenacity. 

The usual rule for determining it is this : Multiply 
the square of the diameter of the cylinder in inches, by 
the cube root of the length of the stroke in feet, and 
divide by 47 / the quotient is the horse power. 

Now, the chief object for establishing a rule for 
nominal horse power was to create a commercial unit, 
by which the power of one engine could be compared 
with that of another engine ; and this rule might meet 
the wants of the case, did the lengths and breadths of 
all cylinders bear the same ratio, and did the pressure 
of steam remain an invariable quantity : but as these 
elements are constantly varying, it is of no use what- 
ever ; and further, if they did not vary, the simple 
square of the diameter would express an unit equally 
incorrect. In order to show further the utter useless- 
ness of the term horse power, as expressed above, we 
will take two engines, each having 70 inches diameter 
of cylinder, one 10 feet stroke, the other 5 feet stroke, 
and ascertain the nominal horse power of each. 



152 



VIBRATION OF BEAMS. 



T0 2 X VlO 

47 



224.7 horses. 



70 2 X V 5 

47 



= 178.2 horses. 



Now, then, if the pressure of steam was the same 
in these two cylinders, and the pistons moved with 
the same velocity, it is manifest that the powers must 
be the same ; yet, according to the rule for nominal 
horse power, they are made widely different ; and if 
so much difference is made while the pressure of steam 
is supposed to remain constant, what must we expect 
when that element also varies ? 

Vibration of Beams. 

Given, the length, O e, from centre of beam, to a 5, 
line passing through centre of cylinder =10 feet ; and 



Fig. 13. 




length of stroke =10 feet ; required, the length O A, 
or O C, of half the beam ? 



MAKINE ECONOMY. 153 

The line a b bisects the versed sine of the arc, and, 
supposing one half (c C) of the versed sine to be = a?, 
we have (10 + xf = (10 - xf + 5 2 

100 + 20a? + a? 2 = 100- 20a? + a? 2 + 25 
20a? + 20a? =25 
a? = .625, 

Hence, half the length of the beam == (10 + .625) 
= 10.625 feet. 

Marine Economy. 

A body moving through water with a certain 
velocity displaces a certain quantity of water in a given 
time, with a certain velocity ; if the velocity be doubled, 
the quantity of water displaced will also be doubled, 
because the body moves double the distance, and each 
particle of water will, therefore, be displaced with 
double the velocity ; hence, the resistance to the body 
will be as 2 X 2, or as the square of the velocity. Thus 
it appears that, if a ship consumes 500 tons of coal to 
perform a certain distance, at the rate of 5 miles the 
hour, to perform the same distance at the rate of 10 
miles the hour, would require 5 2 : 10 2 : : 500 : 2000 
tons, or 4 times 500 ; but the quantity of coal required 
for any one day, at the rate of 10 miles, will not be 4 
times the quantity required at that rate for 5 miles, 
but will be 8 times ; for, supposing the speed be in- 
creased to 10 miles the hour, the same distance will be 
performed in 5 days ; hence, we have, in the first case, 
500 tons consumed in 10 days '= 50 tons per day, and 
in the latter case, 2000 tons in 5 days = 400 tons per 
day, or 8 times 50 tons. Now, then, taking the coal 
as the exponent of the power, we see that the power 



154 MARINE ECONOMY. 

has to increase as 2x2x2, or as the cube of the 
velocity. Hence the importance, wherever speed is 
not an object, of running the engines as slow as possi- 
ble, in order to economize the fuel. 

But whenever there is an adverse current to con- 
tend with, the most economical speed is half as fast 
again as the current. That is to say, if the velocity 
of the current be 4 miles the hour, the velocity of the 
vessel should be 6 miles. We will endeavor to demon- 
strate this without the use of mathematical formula. 

Let 1 represent the power required for a speed of 
one mile per hour, then, inasmuch as the power in- 
creases as the cube of the velocity, the power required 
for the speed of 6 miles = 6 3 = 216, and the ground 
moved over = 4 — 2 = 2. 

Suppose, now, the velocity of the ship be reduced 
to 5 miles per hour, the power will be = 5 3 = 125, and 
the ground moved over =5 — 4 = 1. 

Suppose, again, the speed to be increased to 7 miles 
per hour, the power will be =7 3 = 343, and the ground 
moved over = 7 — 4 = 3. 

Summing up these figures, we have for a speed of 
7 miles per hour a power expended of 343, to make 
good a distance of 3 miles = 114^- per mile ; for a 
speed of 5 miles, a power of 125 to make good 1 mile 
= 125 per mile; and for a speed of 6 miles, 216, to 
make good 2 miles = 108 per mile. Consequently, 
the least power is required at the speed of 6 miles, 
which is half as fast again as the current. 

Had the calculation been made for any fraction of 
a mile, either above or below 6, the same result would 
have been obtained. 

These calculations apply alike to head winds, <fcc., 
at sea, as well as to a tide-way in a river ; whence it 



LIMIT TO EXPANSION. 155 

follows that a vessel can be run even too slow for 
economy, but nevertheless, when having a heavy head 
sea to contend with, there are other elements besides 
economy of fuel to be taken into consideration ; the 
strain upon the vessel and machinery, the plunging 
and staving in of the light work about the bows and 
other places, shipping of seas, &c, are matters which 
also require the judgment of the commanding officer. 

Limit to Expansion. 

Theoretically, supposing a perfect vacuum to ob- 
tain in the cylinder, there is no limit to expansion ; 
but, practically, there is. The unbalanced pressure at 
the end of the stroke should never be less than suffi- 
cient to overcome the friction of the engine, and ought 
always to be a little more. 

Example. — Length of stroke = 8 ft. ; initial pres- 
sure of steam 30 lbs. per square inch, inclusive of the 
atmosphere ; back pressure 4 lbs. per sq. inch ; friction 
of engines, &c, = 2 lbs. per square inch ; required the 
point where the steam should be cut off to yield all its 
useful effect ? 

x = the point, 
4 + 2 = 6 = the pressure at the end, 

x X 30 = 6 X 8 
30# =48 

x = 1.6 ft. from commencement. 

The Proper Lift for a Valve 

Is equal to the area of the valve divided by the 
circumference. 



156 TEMPERATURE OF COOT)ENSER. 

And the metal of which they are made is either 
brass or cast iron ; the latter has the advantage of ex- 
panding nearer equal with the steam chest. 

Temperature of Condenser, 

Example. — Water in the boilers, carried at a den- 
sity of 1 f per saline hydrometer ; temperature of the 
condenser, and water entering the boilers, 105° Fahr.; 
vacuum in condenser, 27.82 inches. Compare the eco- 
nomic performance of the engine, under these circum- 
stances, with the same engine, carrying ^the water in 
the boilers at the same density, but the water in the 
condenser at 120° Fahr. ; the mean pressure of steam 
in both cases on the piston being 20 pounds per square 
inch? 

Solution. — Neglecting the difference of power in 
the two cases required to work the air-pump, taking 
the boiler pressure at 20 lbs., and 2 inches of mercury 
to be equal to 1 lb. pressure, we proceed thus : 

1184-105X.75+228.5-105 : 228.5-105 : : 100 : 
13.23 per cent, loss by blowing off, in the first case. 

1184-120X.75+228.5-120 : 228.5-120 : : 100 : 
11.96 per cent, loss by blowing off, in the second case. 

* 20x2 : 2.18 (back pressure) : : 100 : 5.45 per cent, 
of the effect of the engine lost by back pressure, in the 
first case. 

20 X 2 : 3.33 (back pressure) : : 100 : 8.325 per cent, 
of the effect of the engine lost by back pressure, in the 
second case. 



TEMPERATURE OF CONDENSER. 15*7 

Now, then, letting the fuel represent the power, 
we observe, in the first case, that only (100 — 13.23=:) 
86. 77 per cent, reaches the engine, of which 5.45 per 
cent, is lost in back pressure, and 5.45 per cent, of 
86.77 per cent. =4.7 3 per cent, of the total effect lost 
by back pressure, leaving (86.77—4.73=) 82.04 per 
cent, to be applied to operating the engine. 

In the second case, (100— 11.96=) 88.04 per cent, 
of the power reaches the engine, of which 8.325 per 
cent, is lost in back pressure, and 8.325 per cent, of 
88.04 per cent.=7.33 per cent, of the total effect lost 
by back pressure; leaving (88.04 — 7.33=) 80.71 per 
cent, to be applied to operating the engine. 

Therefore, under the conditions of the example, 
the engine, in the first case, performs the same amount 
of work with (82.04 — 80.71=) 1.33 per cent, less fuel. 

This calculation can be made accurate by taking dia- 
grams from the cylinder and air-pump, under the con- 
ditions of the example, and estimating the power in 
each case ; then, the power to work the air-pump is 
considered. 



CHAPTER VI. 

WESTERN RIVER BOAT ENGINE. 

Fig. 1 is a side elevation, and Fig. 2 an end view of 
the celebrated high-pressure engine, so extensively 
employed on all the Western rivers, also in many iron- 
rolling mills, and other manufacturing establishments 
of the West. 

The first steamboat that ever navigated the great 
rivers Ohio and Mississippi was called the New Or- 
leans, built at Pittsburgh, Pa., by Mr. Eosevelt, for 
Messrs. Fulton & Livingston, of New York ; launched 
March, 1811, and made a passage to New Orleans the 
latter part of the same year. We have no reliable 
information in regard to the kind of machinery used 
on board that boat. The type at present employed, 
however, came into use early in the history of Western 
river steam navigation. It subsequently underwent 
several modifications, but for a quarter of a century it 
has been made essentially as represented by the fol- 
lowing cuts. In fact, so alike have they been made, 
for many years, that those engaged in constructing 
them make no drawings, but continue from year to 
year to cast from the same patterns, and make and 
erect without variation. 

In all the side-wheel boats, the engines are discon- 
nected, separate, and distinct, so that by revolving the 
wheels in opposite directions, the boats can be turned 
©n a pivot. 



rn 



WESTERN RIVEK BOAT ENGINE. 



159 




** fe— -i~e 



11 



Section through X K 



160 



WESTERN RIVER BOAT ENGINE. 



Fig. 2. 




Section through W Z. 



EXPLANATIONS OF DIAGRAMS. 

The piston is represented to be proceeding in the 
direction indicated by the arrows, both steam valves 
closed and one exhaust valve open ; the steam is there- 
fore cut off, and acting expansively. 

Like letters refer to like parts in both views : 
A, steam cylinder ; B, stearo, piston, with metallic 
packing set out with springs, as recently introduced ; 
c c, piston follower ; 2>, piston rod ; E F, steam side 
pipe, to which the steam pipe from boilers is attached ; 
FF, steam valves ; G : exhaust valve ; H H, valve 



WESTERN RIVER BOAT ENGINE. 161 

stems; II, valve levers; K K, steam valve lifters; 
L L\ arms connecting steam rock shaft with exhaust 
lifters, on opposite side of engine, shown in Fig. 2 ; 
N N, points of application of weight or pressure to 
levers • P P, fulcrums of levers ; jS, steam rock shaft 
arm, to which cut off cam rod is connected ; T T, pins 
of rock shaft arms, to which full stroke cam rod is 
hooked ; S, starting bar. 

The lifters for working the exhaust valves, with 
arm L cast on, are loose, and vibrate on the steam 
rock shaft. They are on the opposite side of engine, 
as shown in Fig. 2. The arms L L are of the same 
length, being used only to connect the exhaust rock 
shaft to the exhaust lifters. 

The valves are worked by cams ; the exhaust cam 
being made for fall stroke, and the steam cam to cut 
off the steam at defined points of the stroke. 

There is a short shifting link to connect the ex- 
haust rock shaft arm at jTwith the steam rock shaft 
arm i?, so that when it is desired to work the steam 
full stroke, instead of expansively, it is only necessary 
to unhook the steam cam rod from the pin on the arm 
i?, and hook on the short link ; thus connecting all 
the valve levers, and working all the valves by the 
full stroke cam. To back the engine, the engineer has 
only to shift the full stroke cam rod from the lower 
pin T to the upper pin T. The laborious working of 
the engines by hand is therefore entirely avoided ; and 
as there is much backing to be done at the different 
landings, this is of importance. 

The pitman (connecting rod) is of wood strapped 
with iron, and from 3 to 4 times the length of stroke. 

The valves are of cast iron, sometimes double and 



162 WESTERN RIVER BOAT ENGINE. 

balanced, but most frequently single and unbalanced, as 
represented in the diagrams. In the latter case, con- 
siderable power is expended in working them against so 
high a pressure, unless the valve gear be constructed 
to reduce the power to a minimum at the point of its 
application. This, however, is not often done, though 
it can be so arranged. And, as a matter of exercise 
for the student's mind, we will give some explanation 
of it, and of the operation of the valves. 

The gear may be considered a compound lever, or 
two connected levers, transmitting the power from the 
cam rod pins through each other to the point of resist- 
ance, weight, or pressure. The explanation, then, is 
as follows: Call lever I No. 1, and lifters K iTlever 
No. 2 ; say the length of the long arms of the levers 
are 64 and 9 inches, and the short arms 16 and 3 
inches. That is, the distance from fulcrum P of lever 
No. 1 to the end or point where the lifter first touches 
it and begins to raise the valve is 64 inches, and the 
distance from centre of steam rock shaft, which is the 
fulcrum of lever No. 2, to cam rod pin centre is 9 
inches ; also that from P to JVJ of lever No. 1, is 16 
inches, and from centre of steam rock shaft of lever 
No. 2 to point on lifter where it commences to raise 
the valve lever is 3 inches. Now, suppose there to be 
a pressure of 140 lbs. per square inch in the pipe E \E, 
consequently on the valves, and that the diameter of 
the valve is 6 inches, there is hence a pressure on each 
valve of 6 X 6 X .7854 = 28.274 x 140 == 3958.36 lbs., 
which, added to weight of valve and lever, weighed at 
N, say 40 lbs. more, == 3998.36. This will be reduced 
at 7, end of lever No. 1, to 3998.36 -f- 4 = 999.59 lbs., 
and at the pin of steam rock shaft arm to 999.59-1-3 



WESTERN RIVER BOAT ENGINE. 163 

= 333.196 lbs. required to operate the valves, friction 
not included. Or the work may be shortened by mul- 
tiplying all the long arms together, all the short arms 
together, dividing one by the other, and the weight 
by this result, thus : 

64 x 9 

jt. q = 12, and 3958.36 + 40. + 12 = 333.196. lbs. 

To work the engine by hand, this weight can be 
reduced by the length of starting bar to say 54.97 lbs. 
And it can be further reduced by closing the exhaust 
valves sooner, so as to partially balance the steam 
valves : for instance, suppose they be closed when the 
piston is in the position to leave 6 inches between it 
and the cylinder head ; that there is a clearance of f 
of an inch, and that the back pressure against the pis- 
ton is 5 lbs. per square inch when the valve is closed ; 
now, according to the law of expansion and compres- 
sion of gases, when the piston has travelled 3 inches 
further, or half the distance from point of closing the 
valve to cylinder head, there will be a pressure against 
it of 10 lbs. per square inch, and when it has travelled 
1£ inches further, there will be a pressure of 20 lbs. 
per square inch, and when f of an inch further, or at 
end of stroke, there would be a pressure of 40 lbs. per 
square inch for the piston to cushion against, but the 
valve is not relieved to this extent if it has any lead ; 
say it is opened 1J inches before the piston arrives at 
the end of its stroke, we then have only 20 lbs. per 
square inch pressure under the valve to be deducted 
from the 140 lbs. per square inch above it, or a total 
steam pressure on the valve of 3390.08, instead of 
3958.36. 

We have been considering the power necessary to 



164 WESTERN RIVER BOAT ENGINE. 

work each steam valve separately : we will now con- 
sider that requisite to operate each exhaust valve. 
The proportion of levers and gear remaining the same, 
the steam cut off at half stroke, and the diameter of 
valve *l\ inches — this being the ratio considered neces- 
sary for the free and quick escape of the steam — there 
will consequently be by the reduction of pressure com- 
mon to expansion, at the time the valve is to be opened, 
70 lbs. per square inch on it, or in round numbers 
1979.18 lbs. less than on the steam valve. To cut off 
shorter, this pressure is still further reduced ; to follow 
longer, it is increased — the reduction of pressure and 
temperature by leakage and condensation in the cylin- 
der not being considered. 

This type of engine is peculiarly adapted to the 
boats on which it has been exclusively employed 
for more than quarter of a century ; and when well 
constructed, correctly proportioned, and properly man- 
aged, it performs the work satisfactorily, can be han- 
dled with facility, is durable, and could be made eco- 
nomical. But all these elements are seldom found in 
any of them. The valve gear is generally arranged so 
that the valves cannot be worked by hand against the 
full pressure on them ; the steam valves are set with 
little or no lead, and the exhaust valves do not close 
until the piston arrives at the end of the stroke, so 
that there is only a very small cushion against the pis- 
tons at the end of the cylinders, and the cranks pass 
the centres against an unbalanced pressure of from 50 
to 60 lbs. pressure per square inch. The cams for 
working the steam valves are usually made to cut off 
the steam at half, five-eighths, or three-quarters from 
commencement of stroke ; and the cylinders, steam 



WESTERN RIVER BOAT ENGINE. 165 

pipes and drums, upper portions of boilers, etc., are 
always uncovered (not jacketed) by non-conducting 
substances, and exposed to the cold winds sweeping 
between the decks. It will therefore be seen that a 
large margin is left for improvement in proportions, 
and more so for saving fuel. The temperature of the 
steam in boilers, pipes, etc., may be averaged at 360° 
Fahrenheit, and the temperature of the atmosphere 
during the year at 60° ; hence there is a difference be- 
tween the temperature of steam within the vessels and 
the atmosphere outside of 800° ; and considering the 
unusual large radiating surface exposed to the winds 
and cold air, the loss from the condensation of steam 
in cylinders, pipes, etc., cannot be less than 15 per 
cent, of the fuel consumed. And the saving which 
could be realized in fuel from a high degree of expan- 
sion, where the pressure is about 140 lbs. per square 
inch, may be estimated by the student from calcula- 
tions under that head commencing at page 12 of this 
work. 

The lifter represented in the diagrams was intro- 
duced not very long ago, and patented by Mr. A. Har- 
tuper, of Pittsburg, Pa. It is a great improvement 
over the lifter formerly employed and still used to a 
great extent. 

The improvement consists in commencing to lift 
the valve lever close up to the rock shaft, and starting 
With an easy curve from the horizontal centre line of 
the rock shaft downward. Its advantage is to be found 
in a smooth-working valve gear, and reduced power 
to work the valves consequent on the reduced distance 
between the fulcrum of lever No. 2 and application of 
power on lever No. 1 ; that is, between the centre of 



166 WESTERN RIVER BOAT ENGINE. 

rock shaft and point where the lifter first touches the 
lever and begins to raise the valve. The valve once 
started from its seat, steam rushes under it, and assists 
its ascent; hence, as the bearing point of the lifter 
approaches its end, the valve becomes balanced from 
the steam under it. Furthermore, the shape of the 
lifter is such as to raise the valve quickly. 

The ordinary lifter begins to raise the valve lever 
from and near its end, and several inches from the end 
of lever I, instead of near the fulcrum of lever No. 2, 
and at the end of lever No. 1. It will therefore be 
readily seen that, if this lifter should be substituted 
for the one represented in the drawing, the power to 
work the valves would be greatly increased. As an 
illustration, suppose the arms K Kto commence lift- 
ing 12 inches from centre of rock shaft, and 9 inches 
from end of lever No. 1, then there would be a power 
of 1160.9 lbs. required at I, and 1546.78 lbs. at the 
end of arm H. 

In addition to this increased power to work the 
valves, the sudden striking of the valve levers by the 
old-fashioned lifters is objectionable, and involves the 
necessity of putting a leather shoe on the lever to ease 
the disagreeable noise. 

In explanation of the reduction of power conse- 
quent upon the combination of levers, the student 
must bear in mind that what is gained in power is 
lost in time, the lifters being but a short space of time 
raising the valves, during the stroke of the engine. 

The kind of lifter represented in the diagram, Fig. 
1, but with much greater curve downward, is some- 
times used on land engines, and operated by the eccen- 
tric to cut off the steam at defined points of the stroke, 



WESTERN EIVER BOAT ENGINE. 167 

in the same manner as the Stevens cut off; namely, by 
lost motion, or, in other words, by causing the toes to 
travel a considerable distance before commencing to 
raise the valves. 

In order to get a clear understanding of this, the 
student can refer to the diagram of the Stevens cut off, 
page 22, and consider the steam-lifting toes B B, in 
that diagram, in the same light as the valve levers II 
of Fig. 1 in the. above. The principle on which the 
two kinds of cut offs are operated is precisely alike, 
the only difference being that one is made adjustable 
and the other is not. 

Some of the boats plying on the upper rivers have 
stern wheels, i. <?., one paddle wheel applied at and 
projecting over the stern the whole width of the boat. 
Many of such of 300 tons burthen draw only from 16 
to 20 inches of water : lightness of machinery, compat- 
ible with strength, is therefore of the first importance 
in such vessels. The boilers of all of them are, as a 
rule, placed near and fronting the bow ; and as the 
stern wheel variety involves the necessity of placing 
the engines near the stern, the steam pipes are as a 
consequence exceedingly long, not unfrequently from 
90 to 100 feet or more, thus causing still further loss 
from condensation of the steam. It is proper, however, 
to remark, that when coal can be furnished, as it is on 
the upper rivers, at less than one dollar per ton, econ- 
omy of fuel is a secondary consideration. It is also 
proper to state that the owners and operators of the 
boats are slow to make improvements in their steam 
machinery, even when the advantages of such can be 
practically demonstrated. As an instance of this, we 
may mention that spring cylinder piston packing, so 



168 WESTERN RIVER BOAT ENGINE. 

long successfully applied to the pistons of all types of 
engines, is now, the year 1862, introduced in the river 
engines for the first time. 

It is to be regretted that the Indicator, engine reg- 
isters, and correct guages have not come into use, and 
records kept on board of some of the boats, so that 
correct data for calculating their efficiencies and com- 
parative economy could be had. If w£ are not misin- 
formed, Mr. S. H. Gilman is the only engineer who ever 
applied the Indicator and made experimental tests for 
the purpose of getting correct results from the Missis- 
sippi steamers. Among the few records kept by him, 
we select for the benefit of those interested that of the 
" Magnolia," one of the finest and largest steamers ply- 
ing on the lower Mississippi when the record was taken, 
namely, in the year 1853, and published immediately 
afterward in the " Franklin Institute Journal." 

The diagrams taken from the cylinders of that ves- 
sel showed the valves to have been set without lead, 
and that the engines passed the centres with the un- 
balanced pressure of 60 lbs. per square inch ; the 
stroke being 10 feet, and the steam following the pis- 
tons 6 feet before being cut off — that is to say, both 
the steam and exhaust valves opened and shut pre- 
cisely at the end of the stroke, and that the steam was 
expanded down to 60 lbs. pressure above the atmos- 
phere when the pistons reached the ends of the cylin- 
ders. 



WESTERN RIVER BOAT ENGINE. . 169 



Dimensions and Proportions of the Magnolia. 

Length from stem to stern . ; . . . 295 feet. 

Breadth of beam 35 " 

Breadth of floor 28 " 

Depth of hold . 9 « 

Draft of water when light 4 " 

Tonnage, carpenters' measurement . . . .914 tons. 

Diameter of water wheels 40 feet. 

Length of bucket 12 feet 6 in. 

Width of do. 2 feet. 

Revolutions per minute up stream . . . . 13.5. 

Diameter of cylinders 30 inches. 

Length of stroke . .- 10 feet. 

Length of connecting rod . . . . . . 35 " 

Point of cutting off steam from commencement . . 6 " 

Number of boilers . . 6 

Length of each boiler 30 feet. 

Diameter of each boiler . 42 inches. 

Diameter of each flue 16 " 

Grate area 98.4 sq. ft. 

Diameter of each chimney 5 feet. 

Height of chimneys above grates 80 " 

Area over each bridge wall . . . . . 42.7 sq. ft. 

Area of cross section of all flues . . . . . 16.7 " 
Area of cross section of two chimneys . . . 39.3 " 

Heating surface of all the boilers .... 2617.8 " 
Proportion of grate to heating surface . . . 1 to 26.4 

Proportion of grate to area bridge wall . . . 1 to 0.47 

Horse power developed by engines . . . .1229 

The fuel consumed was wood : no correct results 
as regards evaporation, or coal per horse power per 
hour, therefore given. 

In conclusion, we would earnestly direct the atten- 
tion of western engineers to a study of the subjects 
here presented, especially the Indicator and its use. 
We have witnessed some very faulty working engines 
on the Ohio, occasioned principally by the manner of 
working the steam ; i. e., the valves not being opened 
and shut at the proper points of the stroke. On this, 



1*70 WESTERN RIVER BOAT ENGINE. 

everything else being in order, depends the regularity 
of motion and smooth working of the engine. It is true 
that much may be gained by practical tests ; that is, 
by giving more or less lead to the steam valves, and 
by closing the exhaust valves sooner or later to give 
more or less cushion for the pistons to bring up against, 
until the engines are found to perform best ; but nothing 
accurate can be arrived at without the application of 
the Indicator to every cylinder. It is therefore highly 
important that every engineer having charge should 
understand that instrument and its use. The diagrams 
will at first sight doubtless appear intricate and diffi- 
cult to comprehend, by many of those considering 
themselves entirely practical; but a little study of 
chapter 2 of this work, together with a few applica- 
tions of the instrument, and some perseverance, will 
soon overcome all difficulties, and result in a clear un- 
derstanding of the subject, and a high appreciation of 
its importance. 



CHAPTEK VII. 

BOILEES, ETC. 

Boilees being the source from which the power to 
actuate steam engines is derived, it becomes of the first 
importance that not only the best and most improved 
types be used, but also that the proportions be such as 
to secure the highest results. 

Since the introduction of steam to sea and river 
navigation, many varieties of boilers have been de- 
signed, tried, and abandoned, and many others having 
but little merit are still in use. As it is not, however, 
the purpose of these notes to give the history of in- 
ventions, but to assist in directing the mind of the stu- 
dent into a channel of reasoning for himself, we will 
for the present be content with mentioning only a few 
of those now most generally used ; namely, the Martin 
water tube, the horizontal fire tube, and the western 
river boilers. 

In designing a boiler for a steam vessel, there are 
many elements to be considered ; such as cost, proper 
materials, strength to bear the intended pressure, quan- 
tity of steam to be furnished in a given time, space occu- 
pied, weight, circulation of water, durability, facilities 
for cleaning and repairing, requisite water and steam 
room, heating and grate surface, area through flues, 
and area and height of smoke pipe. 



172 



BOILERS, ETC. 



All things being equal, that boiler producing the 
largest weight of steam per given weight of combusti- 
ble is the best boiler ; that is, evaporating the greatest 
number of pounds of water per pound of fuel. By 
combustible is meant that portion of the fuel put into 
the furnaces, minus the ashes, clinker, and refuse re- 
moved. 



Fig. 3. 




Jr 



The above drawing represents a side elevation of 
the water-tube boiler, with the tubes arranged verti- 
cally above the furnaces, as patented by D. B. Martin, 
Esq., late Engineer-in-Chief of the U. S. Navy. 

These boilers are almost exclusively employed in 
the steamers of our navy. 



173 



EXPLANATION OF THE DRAWING. 

The line r s represents side and bottom of the 
ship ; o o «?, boiler keelsons, or timbers on which the 
boiler rests ; a, ash pit ; <?, furnace door ; 5, grates ; d, 
furnace ; m, back connection ; e e, the vertical tubes 
containing the water within them, and surrounded by 
the products of combustion t, arch over furnace ; A, 
line of water level ; \ steam room ; Z, steam chimney ; 
g, passage of gases to smoke pipe ; i, water bottom ; n, 
fire-room. 

These boilers are generally situated in the vessel 
face to face, and separated by a fire room of 8 or 9 
feet, in the fore and aft direction. 

The Horizontal Fire Tube, or common marine 
tubular boiler, has the tubes arranged horizontally 
above the furnaces, containing the products of combus- 
tion within, and surrounded with water. In all other 
respects the two types of boilers can be constructed 
alike. If, therefore, we imagine all the tubes to be 
removed from the boiler represented by the drawing, 
and a set of tubes arranged in it horizontally with the 
smoke and gases passing through them, we have the 
common marine tubular boiler so extensively employed 
in the steamers of all European nations. 

To an inexperienced eye this simple difference of 
arrangement of tubes would doubtless appear of little 
or no consequence ; but as simple as it may seem, it 
nevertheless makes an important difference, in the re- 
sults utilized ; also in many other respects, as will be 
seen from the extracts given below, from a report of a 
Board of four Chief Engineers of the Navy, who, by 



174 BOILERS, ETC. 

the directions of the Navy Department, tested the 
efficiency of the two types of boilers, one of each kind 
having been constructed and placed on board the U. S. 
Steamer " San Jacinto " for the purpose of precisely 
the same shell, both as regards form and dimensions. 
The only difference between them was in the arrange- 
ment of the tubes, one being the English or horizontal 
fire tube ; the other of the water tube type. This ex- 
periment may be considered the most important, and 
certainly the most extensive and accurate ever made 
with marine boilers. 



EXTRACTS FROM REPORT. 

The experiments were made to determine the rela- 
tive evaporative efficiencies of the two boilers, under 
the conditions of actual practice on board marine 
steamers. For this purpose, a short experiment would 
be valueless from the impossibility of knowing whether 
the condition of the fires were exactly the same at the 
commencement and at the end, from the inequality in 
firing ; from the different proportions of refuse found 
in different weights of coal ; from fluctuations in draft ; 
from losses by cleaning the fires ; and from the differ- 
ent quantity of air in proportion to fuel admitted at 
different times. It was therefore considered necessary 
that the experiments with each boiler should continue 
uninterruptedly four days, or 96 hours. 

The weight of water evaporated was ascertained 
from the steam pressure in the cylinders at the end of 
the stroke of piston, as given by the indicator. The 
cost of this evaporation was the weight of combustible 



BOILERS, ETC. 1?5 

consumed. * * * * * * Every pound of coal put 
into the furnace, and every pound of ashes, clinker, and 
refuse removed was weighed each hour. The experi- 
ments were conducted in precisely the same manner 
with both boilers, and as follows ; namely : At the 
commencement, no account was taken of the coal re- 
quired to raise steam, or of the temperature of the 
water in the boilers ; but after the steam was raised 
to 22 lbs. per square inch pressure above the atmos- 
phere, the level of the water in the boiler was noted, 
the condition of the fires estimated as nearly as pos- 
sible by the eye, and the engines started. At the end 
of each experiment, the water in the boiler and the 
condition of the fires were left as at the commence- 
ment. The experiments with both boilers were begun 
and ended at midday, and continued uninterruptedly 
96 hours. During that time, the boiler steam pres- 
sure and the vacuum in the condenser, by barometer 
gauges, were noted every 5 minutes ; and at the close 
of each hour there was recorded for that hour the 
mean steam pressure and vacuum ; the temperature of 
the engine room, of the fire room, of the salt and fresh 
water hot wells, and of the injection water; also the 
weight of coal thrown into the furnaces, and the 
weight of dry refuse in ashes, clinkers, and fine coal 
withdrawn. Every hour an indicator double diagram 
was taken from both cylinders, and from the mean of 
the final pressures as given by these diagrams the 
evaporation was calculated. * * * * * * At the 
commencement of each experiment, the boiler was filled 
with sea water ; and at the expiration of every hour 
the saturation was recorded ; also the number of inches 

12 



176 



in depth of water blown off to maintain it at 1 \ times 
the natural concentration. 

The number of double strokes made by the pistons 
were taken by a self-registering counter. 

The same firemen fired both boilers, and the same 
engineers directed them. The experiments were first 
made on the Horizontal Fire-Tube Boilers ; they were 
begun at noon on the 10th of June, 1859 ; and after 
being completed, the steam was shut off from it and 
let on from the Vertical Water-Tube Boiler, without 
stopping the engines. The coal was Pennsylvania an- 
thracite. 



Results of the Experiments. 





En^li^h Horizon- 


Martin's Vertical 




tal F, re-Tube 


Water-Tube 




Boiler. 


Boiler. 


Total number of lbs. of coal consumed . 


100436.00 


92512.00 


, " "of refuse ashes, etc. . 


24908.00 


24178.00 


41 "of combustible consumed 


75528.00 


68334.00 


Per centum of coal in refuse .... 


24.80 


26.14 


Mean gross horses power developed by the engines 


187.25 


201.07 


Mean number of lbs. of coal consumed per hour 


1046.21 


963.67 


Mean No. of lbs. of coal consumed per sq.ft. of grate 


9.7 


9.00 


Total No. of lbs. of water evaporated from feed 






water of 100° Fah 


.671813455 


.720 6914 


Pounds of water evaporated from feed water tem- 






perature of 100° Fah. by 1 lb. of coal . 


6.7 


7.8 


Pounds of water evaporated from feed water of 




> 


100° Fah. by 1 lb. of combustible 


8.9 


10.6 



Comparative Advantages and Disadvantages. — 
We are directed by your order to report to the De- 
partment the relative advantages and disadvantages 
of the two kinds of boiler as regards space occupied, 
weight, cost, accessibility for cleaning and repairs, du- 
rability, evaporative efficiency, and the relative quan- 
tities of steam that can be furnished in equal times. 

1st : As regards space. — In the particular specimens 



177 

experimented on, the space occupied by both, types of 
boiler was equal, but not so the area of contained 
heating surface. If the proper measure of that surface 
be, as we think it is, the extent exposed to the recep- 
tion of heat from the products of combustion, then the 
heating surface in the vertical water-tube boiler ex- 
ceeded that in the horizontal fire-tube boiler by nearly 
23| per centum of the latter. If, however, it be meas- 
ured by the extent from which water is evaporated, 
then the superiority will still remain with the vertical 
water-tube boiler, but reduced to 7^ per centum. 

2d : As regards the weight of the two Boilers. — By 
referring to the table of their dimensions and weights, 
it will be seen that in this respect the experimental 
boilers were nearly equal, the horizontal fire tube hav- 
ing a slight advantage in lightness ; but if the aggre- 
gate weight of boiler and contained water at the 
steaming level be compared, then the vertical water 
tube has a superiority of nearly 5 J per centum over its 
competitor. 

3d: Cost. — In this particular the horizontal fire- 
tube boiler is slightly the cheapest, but the difference 
is unimportant. 

4th : Accessibility for cleaning and repairs. — For 
the removal of scale or any insoluble sediment on the 
water surfaces of the tubes, the vertical water-tube 
boiler has a decisive superiority from the complete 
and easy manner in which the entire of those surfaces 
can be reached by a scaling tool and cleaned mechani- 
cally. With the horizontal fire-tube boiler this ope- 
ration is very tedious and difficult, and at the best is 
only partial. It may indeed be said that the whole 
of the horizontal tubes cannot be scaled without the 



178 BOILERS, ETC. 

removal of a portion of them ; and from the fact of 
their becoming more and more coated with scale as 
their age increases, their evaporative efficiency will be 
continuously impaired to the extent of the loss of heat 
thus intercepted. On the other hand, the horizontal 
fire tubes are much more easily and completely swept 
of soot and deposit from the furnaces ; they are also 
more easily plugged when leaking. Furthermore, they 
are only about one fourth the number of the vertical 
water tubes, and the liability to leakage is correspond- 
ingly lessened, but this liability is so trifling as to be 
of no* value in a practical estimate. The remaining 
portions of both boilers are equally accessible for clean- 
ing and repairs. 

5th : Durability. — We have no data on which to 
base an opinion in this respect, but we believe both 
boilers to be about equal. 

6th : Evaporative Efficiency. — The relative evapo- 
rative efficiency, as given by the experiments, applies 
rigorously only to the particular specimens of the types 
of boiler employed, with their peculiarities of propor- 
tion and under the conditions of the trials ; under other 
conditions and with other proportions, the relative 
evaporative efficiency would doubtless be different, 
and in direction as determined by better or worse pro- 
portions, and by conditions more or less favorable for 
one kind of boiler over the other. The proportions 
given to both boilers in the present case, however, are 
such as are now generally approved in practice. With 
these proportions and under the actual conditions of 
the trials, the evaporative efficiency of the vertical 
water-tube boiler exceeds that of the horizontal fire 
tube by 18 J per centum of the evaporation of the lat- 



WESTERN RIVER BOILERS. 179 

ter, making the comparison by weight of combustible 
consumed; and by 16 J- per centum if the comparison 
be made by weight of coal consumed ; the former is, 
of course, the proper result. 

7 th : Relative Quantities of Steam that can he fur- 
nished in equal times by the two Boilers. — In this 
respect the superiority remains with the horizontal 
fire-tube boiler, in which the combustion of the fuel 
can be forced to a considerably greater extent than in 
the vertical water-tube boiler. The additional steam, 
however, thus obtained will be at a greater pro-rata 
cost of coal, but we have no data to determine either 
the increased quantity or its increased cost. 

Finally, in view of the much greater evaporative 
efficiency of the vertical water-tube boiler, and of the 
facility and completeness with which it may be scaled, 
• — the two qualities of paramount importance with 
marine boilers, — we would express our decided opinion 
that its superiority over the horizontal fire-tube boiler 
is so strongly marked as to unquestionably entitle it 
to the preference. 

WESTERN RIVER BOILERS. 

The first steamboat constructed for the western 
rivers had cylindrical boilers. Since that date, many 
types of boilers have been made, and tried on board 
some of the many steamboats navigating those immense 
inland waters ; but none of them, except those repre- 
sented by the following drawings, have ever gained 
general favor. In consideration of this fact, of the 
great number constructed every year at different 
places on the rivers, and of the high pressure of steam 
used, they deserve more than a passing notice. 



180 



WESTERN EIVEB BOILEES. 




Transverse Section through Front Elevation. 

Fire Bed. 




Longitudinal Section through A B of Front View. 



WESTERN RIVER BOILERS. 181 

DESCRIPTION OF DRAWINGS. 

a, asli pit ; b, furnace doors ; e, grate bars ; J, flues ; 
E ) smoke pipe ; 6r, steam room ; F, steam drum ; H, 
mud blow pipe ; 7, feed ; K, brick work. 

The safety valve is put on the top of the boiler 
shell. These boilers are placed side by side on the 
deck of the vessel, near ,-icl fronting the bow, ar- 
ranged in numbers from one to eight, according to the 
size of the boat. 

The fronts are of cast iron, resting on the deck ; 
the back ends are also supported by cast brackets 
under the feed. Brickwork surrounds the outside, and 
also forms the bottom of the lower smoke flues. 

The only variations from the drawing ever made 
in these boilers, consists in the diameter and length of 
shells, and diameter and number of flues. 

The majority are two-flued ; but they are made 
with four, five, and six flues, varying in diameter from 
5 to 18 inches each. The shells are made of 44, 42, 
38, 36, and 34 inches diameter, with lengths varying 
from 32 to 22 feet. The iron used in the shells of the 
two largest diameters is ^ T of an inch thick, but for 
those of 40 inches diameter and under it is never more 
than \ inch thick; for the smallest sizes it is even 
occasionally ^ T thick. In the largest flues it is some- 
times T V of an inch thick, but for all medium sizes it 
is \ inch. The heads are all wrought iron, generally 
-f of an inch thick, with the flanges turned on the 
front one. 

All the seams are single riveted, with \ rivets, 
many of which are driven cold in all seams accessible 
for the purpose. 



182 WESTEE^ PwIVER BOILEES. 

The maximum pressure of steam carried on these 
boilers is about 150 lbs. per square inch ; but, prior 
to the law limiting the pressure, from 200 to 220 lbs. 
per square inch was not an unusual daily working 
pressure on a boiler of 40 inches diameter of shell, and 
i inch thickness of iron, such as the above drawing 
represents; and although many explosions occurred 
and flues were collapsed during the early days of west- 
ern river steam navigation, yet all of them have been 
attributed either to defective materials, imperfect work- 
manship, incompetent and reckless engineers, or to the 
omission of steam pumps (Doctors, as they are called 
by western engineers) to supply the boilers with 
water during the time that the boats were landing 
passengers and freight at the different stopping points. 

All the iron from which they have been constructed 
within the past few years has been made from cold- 
blast charcoal pigs, worked into blooms in charcoal 
furnaces. The rivets are also made from the best char- 
coal blooms. In fact, their success as regards safety 
may in a great degree be attributed to the superior 
quality of the materials used in their construction. 

The lifetime of the boats in which they are em- 
ployed is averaged at five years, and when they cease 
to be fit for use, the engines are transferred to a new 
boat — sometimes to a third, and occasionally to a 
fourth boat : the boilers are never used on the second 
boat, but always removed to the shore, and worked at 
reduced pressures — the objections to their further use 
on board vessels being their reduced strength conse- 
quent upon a chemical change in the iron, occasioned 
by the high temperatures. Hence extreme and varied 
expansions and contractions ; this causes crystallization. 



WESTERN RIVER BOILERS. 183 

and the sheets to crack through the line of the rivet 
holes where the laps come directly in contact with the 
greatest heat. To double rivet the seams, or increase 
the thickness of iron, increases the evil ; to cut out 
the defective piece and replace it with a new piece of 
iron starts fresh leaks, because there is a difference 
between the expansion of the old and new metal. The 
only remedy is to remove one circle of sheets. 

The products of combustion are discharged into 
the smoke pipes at such a high temperature that it 
involves the necessity of making the pipes in area of 
cross section about twice that of the flues. The dis- 
tance between the grates and bottoms of boilers does 
not often exceed 16 inches. The coals are frequently 
piled up in the furnaces to the boilers, and consequent 
upon the extreme height (sometimes 80 feet) of the 
pipes, assisted by a blast of steam discharged into the 
back end of the flues, or the exhaust steam admitted 
into the chimneys on the locomotive fashion, the draft 
is very strong, the combustion rapid, and the heat 
applied to the boiler iron intense. There are no com- 
bustion chambers or provision for admitting air through 
holes into the furnace doors or back of the grates. The 
coal is highly bituminous, used extravagantly, and as a 
consequence produces large volumns of dense black 
smoke. The cheap rate at which this coal is furnished 
is the only excuse for making no efforts to economize 
it and prevent the smoke nuisance. 

We feel convinced that time must effect an entire 
change in the mode of ^eneratinc: steam on the western 
waters, for it is evident that tubular boilers can be 
constructed suitable to the purpose, that will not only 
be lighter and more durable, but that can be operated 



184 BOILER FLUES. 

with 50 per cent, less fuel than those now in such high 
favor. 



BOILER FLUES. 

The well established law that the strength of cyl- 
inders is inversely as their diameters, and the hitherto 
undisputed axiom among practical engineers that cyl- 
indrical tubes or boiler flues when subjected to uniform 
external pressure were equally strong in every part 
regardless of length, led to erroneous opinions regard- 
ing the strength of boiler flues. For flues to collapse 
under the ordinary working pressure of steam, in what 
was supposed to be properly proportioned and well 
made boilers, was formerly not an unusual occurrence ; 
and although many theories were advanced on the 
subject, it was not until the celebrated English engi- 
neer, William Fairbairn, LL.D., F. R. S., made an ex- 
tensive set of experiments on the strengths of tubes of 
various forms, sizes, and lengths, that the hidden weak- 
ness was revealed. These experiments were made by 
hydrostatic pressure, applied both externally and inter- 
nally, to test the strength under ordinary conditions 
of practice, and they proved conclusively that the 
strength of flues exposed to external pressure, as ordi- 
narily used, is inversely as the length; that is, a flue 
30 feet long will collapse with just half the pressure 
of a flue 15 feet long, everything else being equal; in 
other words, a flue 30 feet long, which would bear a 
pressure of 100 lbs. per square inch, if shortened to 15 
feet, or, what is the same thing in effect, if it be hooped 
in the middle of its length by angle or T iron, it will 
then bear a pressure of 200 lbs. per square inch. 



BOILER FLUES. 185 

If this important law had been familiar to the en- 
gineer who designed the boilers of the " Great East- 
ern," the disastrous accident which attended the first 
trial of that vessel would have been entirely avoided. 
It will be remembered that the smoke pipe of that ship 
was surrounded by a water jacket for the purpose of 
increasing the temperature of the feed water previous 
to entering the boilers. This jacket contained a column 
of water nearly forty feet in height, and the pipe was 
six feet in diameter ; there was consequently a pressure 
of steam in the jacket which, united to the heavy col- 
umn of water at the base, was sufficient to collapse the 
pipe, and cause the fearful accident. 

Another source of weakness in lap joint riveted 
flues must also be noticed ; namely, the deviation from 
a true circle common to the lap. 

Although it had long been established, that a circle 
is the strongest possible form that can be made, and 
that no deviation from it can be made without reduc- 
tion of strength, yet it was not previously known that 
a 9-inch diameter of tube was reduced in strength 
more than one-third by deviating from a circle only 
sufficient to make a lap joint, the ratio being as 1 to 
10 — so proved by the tests. 

These facts are conclusive, in showing the necessity 
of adhering to the true circle for boiler flues using 
high pressure steam. 

In consideration of this, and the reduction in 
strength consequent upon the rivet holes, it will be 
readily seen that the lap-welded flues, which are both 
seamless and round, have superior advantages over 
those now in use on the western waters. 



186 EIVETmG. 



EIVETLNG. 



The weakest point is the measure of strength ; 
therefore, in the construction of steam boilers, the riv- 
eted joints require close attention, and should receive 
the best workmanship. They are either single or 
double riveted', and the holes should not only be 
punched the proportionate distances apart, but should 
exactly correspond with each other, so that no ream- 
ing need be required. 

In the United States there are three mechanical 
modes of uniting the sheets together ; namely, ma- 
chine riveting, and hot and cold hand riveting. On 
the seaboard, all kinds of boilers are riveted by the 
two first-named methods, in both of which the rivets 
are put in hot. West of the Alleghanies, all riveting 
is done by hand, and at Pittsburgh, Louisville, and 
other places, the rivets are driven cold in all places 
accessible for the purpose. 

For the cold process, a superiority is claimed con- 
sequent upon the holes being well filled with the body 
of the rivets ; that is, there can be no contraction — 
hence reduction in the strength and in the rivets' 
diameters after the workmen cease hammering on the 
heads. The reverse must be the case when driven 
hot ; for, in cooling, the diameters are reduced by con- 
traction. Moreover, none but the best quality of iron 
can be used in rivets driven cold ; because, if the iron 
be inferior, it is sure to crack or split through the 
head, each one being tested by the heading. 

For hot riveting, it is claimed that, in cooling, the 
rivets contract in length, drawing the sheets more 



kivetixg. 187 

closely together, thereby creating adhesion sufficient 
to add to the strength of the joint. Mr. Clarke, Resi- 
dent Engineer of the Britannia Bridge, made some 
experiments to determine the value of this. Three 
plates were riveted together by a machine, maintain- 
ing a temperature of 900 degrees in the rivets ; each 
outside plate had a circular hole in which the rivets 
fitted exactly ; but in the centre one the hole was 
oval, or 2 \ inches long for a £ rivet, and the rivet was 
not allowed to touch either end of this hole. A strain 
was then put on the centre plate till it began to slide, 
which it did abruptly. Several trials were made, and 
the least result was an adhesion equal to 4| tons with 
■i rivets. Mr. Clarke infers from this experiment that, 
by judicious riveting, the adhesion may in many cases 
be nearly sufficient to counterbalance the weakening 
of the plates from punching the holes. In this par- 
ticular we regard his opinion as in error ; for if he had 
continued the strain on the plate until it parted, or the 
rivets broke, he would doubtless have found that the 
total pressure, or breaking strain, would have been 56 
per cent, if single riveted, and 75 per cent, if double 
riveted, of the sheet, as fully tested by other experi- 
ments. Theoretically, there is a gain from adhesion 
in hot-riveted joints, but practically this seems to be 
lost by the contraction of the rivets' diameter, thus 
making the total or breaking pressure the same. 

In our western river boilers, where the pressure of 
steam used is higher than in any part of the world, no 
difficulty has ever been experienced from the cold- 
riveted joints not being closely united and perfectly 
tight ; and as regards strength compared with the hot 



188 RIVETING. 

riveted, superiority is claimed by those having cold- 
riveted boilers in charge. 

In either mode of hand riveting the rivets can be 
seriously injured by too much hammering, and in any 
case by overheating. Due regard should be had to 
the temperature, and the blows of the hammer should 
be hard and quick, and not continued longer than 
necessary to form the head. Machine riveting has the 
advantage of forming the head at a single blow, and 
the rapidity with which the work can be performed 
must always give it preference over all other methods 
where it can be employed. 

It is to be regretted that no extended set of ex- 
periments have ever been made in this country to 
determine the relative strengths of the different modes 
of riveting and uniting the sheets of steam boilers and 
other iron structures ; also to test the relative value 
of the materials used in this country at the present 
day, for it must be evident that although the results of 
European experimenters on iron and steel are of value 
to us, yet they cannot be regarded as entirely applica- 
ble to our constructions, because our iron ores, the 
temperature of blast of smelting furnaces, and manner 
of working the metal through the different processes, 
and the fuel used, all differ in a large degree from 
those abroad. 

In the year 1861 we constructed an excellent hy- 
drostatic machine at the Navy Yard, Brooklyn, N. Y., 
for this very purpose, and were about to commence an 
extended and complete set of such experiments, when 
the war broke out, and we were relieved from that 
station for other duties. 

The only published account of experiments on this 



SUPERHEATED STEAM. 



189 



subject of any value, known to us, are those made in 
England by Mr. Fairbairn, and at Glasgow, Scotland, 
by David Kirkaldy, Esq. 

The following is given by the former author, as ex- 
hibiting the strongest form and best proportions of 
such joints, as deduced from his experiments and ac- 
tual practice. 



Thickness of 


Diameter of 
rivet. 


Length of rivet 


Distance from 
centre to centre. 


Quantity of Lap in 


plates. 


Irom head. 


single riveted. 


double riveted. 


in. 16th. 


in. Ratio. 


in. 


Ratio. 


in. 


Ratio. 


in 


Ratio. 


in. 


Ratio. 


0.19= 3 


0.38= 2 


0.83 


4.5 


1.25 


6 


1.25 


6 


2.10 


10 


0.25= 4 


0.50= 2 


1.13 


4.5 


1.50 


6 


150 


6 


2.50 


10 


31= 5 


0.63= 2 


1.38 


4.5 


1.63 


5 


1.8S 


6 


3.15 


10 


0.38= 6 


0.75= 2 


1.63 


4.5 


1.75 


5 


2.00 


5.5 


3.33 


9.2 


0.50= 8 


0.S1 =1.5 


2.25 


4.5 


2.00 


4 


2.25 


4.5 


3.75 


7.5 


0.63 = 10 


0.94 =1.5 


2.75 


4. 


2.50 


4 


2.75 


45 


4.58 


7.5 


0.75 = 12 


1.13 =1.5 


3.25 


4. 


3.00 


4 


3.25 


4.5 


5.42 


7.5 



SUPERHEATED STEAM 



Is steam, the temperature of which is increased after 
it leaves the boilers. This is generally accomplished 
by passing it through a series of pipes exposed to the 
heat of the discharged gases in the chimney. (See 
drawing of such an apparatus in Nystrom's Pocket 
Book, page 259.) The advantage to be derived from 
the process depends on the condition in which the 
steam leaves the boilers. The theory is — steam gen- 
erated in boilers, and being supplied to engines in 
operation, carries with it to the cylinders water in the 
vesicular state ; that is, in minute globules or innumer- 
able particles ; and that if it be passed through a 
superheating apparatus, these small globules are ex- 
panded into steam, thus utilizing its full effect. This 
vesicular state in which steam is found in boilers when 
in active operation differs more or less according to 



190 SUPERHEATED STEAM. 

the construction of the boilers. In those properly 
proportioned, with elevated steam chimneys, exposing 
much heating surface to the action of the steam, the 
quantity of water carried to the cylinders in this state 
is inconsiderable ; hence, in boilers so constructed, the 
application of a superheating apparatus would not pay 
the extra cost and complication. When, therefore, we 
are informed of large gains in the consumption of fuel 
resulting from the application of such an apparatus to., 
a set of boilers, it becomes necessary to examine the 
construction of the boilers before giving credit of the 
results to superheating the steam. 

In some steamers (and this applies especially to 
many of those belonging to the English), where the 
boilers are very low, and but little height to the steam 
chimneys, gains in the consumption of fuel of from 20 
to 40 per cent, have been effected by the application 
of the superheater ; whereas the same kind of an 
apparatus, if applied to some of our Hudson River 
steamers, would not probably make an average gain of 
5 per cent. 

In the summer of 1854, by the invitation of E. K. 
Collins, Esq., we witnessed some extensive experiments 
on superheating steam, on board the splendid, but ill- 
fated U. S. Mail Steamship "Arctic," In this case, 
the superheating steam pipes were carried down the 
back connexions and through the furnaces close to the 
arches, connecting in the engine room to one common 
chamber, to which a branch pipe from the usual main 
steam pipe was also attached. Thus the arrangements 
were perfected to work the steam : 1st, in the usual 
way, and at the ordinary pressure and temperature ; 
2d, in a highly heated condition, from the pipes passing 



DRAFT. 191 

through the furnaces ; 3d, at a medium temperature, 
that is, the highly heated steam mixed in the chamber 
with the ordinary working steam. So that a fair op- 
portunity was offered, on a large scale, to test the ben- 
efit to be derived from superheating the steam to 
various temperatures ; and the results of the trial 
proved conclusively that the saving of fuel would not 
pay the expense of the apparatus on board that vessel, 
'to say nothing of the labor of keeping it in order. 

This vesicular state in which steam is found in 
boilers must not be confounded with foaming or 
priming, explained at page 81. 



DRAFT. 

Draft is produced by the difference of temperature 
between a column of heated, consequently rarefied air, 
in a chimney, and the surrounding atmosphere ; and 
this draft will be strong and effective just in propor- 
tion to the difference of temperatures and the height 
of the column. The cold and heavy column outside 
the chimney presses down, and forces up the warm 
and light column within. The greater the difference 
between the weight of these two columns the greater' 
will be the draft. A column of two feet high rises, or 
is pressed up, with twice as much force as a column of" 
one foot, and so in proportion for all heights to a cer- 
tain extent, just as two or more corks strung together 
and immersed in water tend upward with proportionally 
more force than a single cork. In a chimney where a 
column of hot air one foot in height is one ounce 
lighter than the same bulk of external atmosphere, if 
13 



192 DRAFT. 

the chimney be fifty feet high, the air and smoke in it 
is propelled upward with a power of fifty ounces. 

In a correctly proportioned chimney, the area of 
cross section of the flues — smoke passage — should grad- 
ually contract from "bottom to top, being the widest at 
the bottom and smallest at the top; because at the 
base the hot column of expanded air and gases fills the 
entire passage, but in ascending they gradually cool 
and contract, occupying less space. 

There is a limit to the useful height of a chimney, 
consequent upon the friction of the heated air and 
products of combustion, and this limit is dej)endent on 
the temperature of the discharged gases compared to 
the area of cross section of the chimney. 



APPENDIX. 



MATERIALS. 

There is no subject connected with the Engineer- 
ing profession more important to be understood than 
materials. Yet young engineers rarely give it study, 
and but few of those in the higher grades have a 
thorough knowledge of the materials used in the con- 
struction of steam machinery; indeed, many cannot 
distinguish the best from the inferior quality of pig 
metal, composition of copper and tin from copper and 
zinc, or charcoal flange boiler plate from ordinary 
puddle plate. 

It is in a large degree owing to this fact that we 
have had so many break downs in our sea-going steam- 
ers, and that the weights of those parts made of 
wrought and cast iron are so much in excess of what 
is necessary for the best materials. "We have, there- 
fore, concluded to devote a short space to this branch 
of the profession, solely with the view of directing the 
mind of the young engineer to this channel as one of 
his studies. 

Some of the following has been extracted from the 
Army Ordnance JVfanual, and all of it accords with 
our experience of many months among the various 



194 cast iron. 

iron rolling mills, furnaces, and steel works of Penn- 
sylvania. 

IRON. 

Of all the useful metals none plays so important 
and extensive a part in the steam engine as iron. It 
is obtained from ores, in which it generally exists in 
the state of an oxide combined with earthy or stony 
matters, and frequently with carbon, phosphorus, sul- 
phur, arsenic, magnesia, manganese, &c. Iron ores are 
classed and named according to their combinations, as 
magnetic, specular, clay iron-stone, red hematite, and 
brown hematites — the last named is the ore from 
which th.e Salisbury and Juniatta irons are extracted, 
the first from which the Swedish iron is obtained, 
and the clay iron-stone that from which the greater 
portion of English iron is made. For producing some 
varieties of pig, different kinds of ores are mixed. The 
foreign substances which iron is found to contain mod- 
ify, in a marked degree, its essential properties. Car- 
bon adds to its hardness, but destroys some of its 
characteristic qualities, and produces cast iron or steel, 
accordiog to the proportion of carbon it contains ; sul- 
phur renders it fusible, difficult to weld, and brittle 
when heated — hot short Phosphorus renders it cold 
short, but may be present in very small proportion 
without effecting injuriously its tenacity. 

CAST IRON. 

The process of making cast iron depends much on 
the kind of fuel used — charcoal, coke, bituminous and 
anthracite coals are all used, and the quality of pig 
metal is influenced to a great extent by the kind of 



CAST IRON. 195 

fuel, as well as by the temperature of the blast with 
which the ore is reduced. When anthracite coal is 
employed, the ore is placed at once into the blast fur- 
nace. When charcoal is used, the ore is first roasted, 
by distributing it in alternate layers with waste coal, 
wood, or, sometimes, with charcoal, and the pile thus 
formed is ignited and burned in the open air. For 
the more refractory ores a kiln similar to that used for 
burning lime is required. The ore is rendered, by 
this operation, more porous and easily broken into 
small pieces, by which it is more readily acted upon 
in the smelting furnace. The small pieces would be 
disadvantageous in an anthracite furnace. 

Smelting is the process by which the iron is sepa- 
rated from the refractory substances with which it is 
combined in the ore. It consists in raising the ore to 
a high heat in contact with carbon and a suitable flux 
in the blast or smelting furnace. The flux unites with 
the earthy matter of the ore, forming a glassy sub- 
stance called slag or cinder, and the carbon unites with 
the oxygen of the ore, setting the iron free, which in 
turn unites with a portion of the carbon and forms a 
fusible compound, carburet of iron, or cast iron. 

The melted iron and slag descend to the bottom 
of the furnace, the slag forming a covering to the pool 
of iron and protecting it from the action of the blast. 
As they accumulate, the slag runs off over the dam, 
and is a good indication, to an experienced eye, of the 
quality of metal the furnace is making. 

The furnace is generally tapped once every twelve 
hours, and the metal is run out into channels formed 
in the sand, and is known ^ pigs. 

Limestone is the flux used for most ores ; clay is 



196 CAST IKON. 

sometimes required to mix with ores containing much 
limestone. 

A larger yield from the same furnace, and a great 
economy in fuel, are effected by' the use of a liot blast. 
The greater heat thus produced causes the iron to com- 
bine with a larger percentage of foreign substances, 
and the strength of the cast iron is thus injured. 

Cast iron, for all purposes requiring great strength, 
should be smelted with the cold blast. 

Pig iron., according to the proportion of carbon 
which it contains, is divided into foundry iron and 
forge iron, the latter beiug adapted only to conversion 
into malleable iron : while the former, containing the 
largest proportion of carbon, can be used either for 
casting or for making bar iron. 

There are many varieties of cast iron, differing from 
each other by almost insensible shades ; the two prin- 
cipal divisions are gray and white, so called from the 
color of the fracture when recent. Their properties 
are very different. 

Gray iron is softer and less brittle than white iron ; 
it is in a slight degree malleable and flexible, and is 
not sonorous ; it can be easily drilled and turned in 
the lathe, and does not resist the file. It has a bril- 
liant fracture, of a gray, or sometimes a bluish-gray 
color ; the color is lighter as the grain becomes closer, 
and its hardness increases at the same time. 

White iron is very brittle and sonorous ; it resists 
the file and the chisel ; the fracture presents a silvery 
appearance, generally fine grained and compact. 

Mottled iron is a mixture of white and gray ; it 
has a spotted appearance. 

The pig metal is generally known in our market as 



CAST IRON. 197 

charcoal cold blast, charcoal hot blast, anthracite, and 
coke iron, and the quality is decided on by breaking 
the pigs and examining the fractures. A medium- 
sized grain, bright gray color, lively aspect, fracture 
sharp to the touch, and a close compact texture, indi- 
cate a good quality of iron. A grain either very large 
or very small, a dull, earthy aspect, loose texture, dis- 
similar crystals mixed together, indicate an inferior 
quality. 

Besides these general divisions, the manufacturers 
distinguish more particularly the different varieties of 
pig metal by numbers, according to their relative 
hardness. 

No. 1 is the softest iron, possessing in the highest 
degree the qualities described as belonging to gray 
iron ; it has not much strength, but on account of its 
fluidity when melted, and of its mixing advantageously 
with other kinds of irons, it is of great use to the 
founder, and commands the highest price. 

No. 2 is harder, closer grained, and stronger than 
No. 1 ; it has a gray color and considerable lustre. 

No. 3 is still harder — its color is gray, but inclining 
to white ; it has considerable strength, but is princi- 
pally used for mixing with other kinds of iron. 

No. 4 is bright iron, No. 5 mottled, No. 6 white — 
which is unfit for general use by itself. 

East of the Alleghany mountains, the anthracite 
hot-blast iron is used for all ordinary purposes, and 
west of the Alleghanies coke hot-blast iron is in gen- 
eral use. 

Pig metal is improved by being remelted in an air 
furnace. All cast iron expands forcibly at the moment 
of becoming solid, and again contracts in cooling; 



198 MALLEABLE IRON. 

gray iron expands more and contracts less than other 
iron. 

The color and texture of cast iron depend greatly 
on the size of the casting and the rapidity of cooling ; 
a small casting, which cools quickly, is almost always 
white, and the surface of large castings partakes more 
of the qualities of white metal than the interior. Care 
should always be taken to cool them as equally as pos- 
sible, and not too rapidly. 

West of the Alleghanies, where bituminous coal is 
so plentiful and cheap, air furnaces are in general use 
in foundries, and the castings made from them are 
superior to those from the cupola furnace, as l was 
proved at Pittsburg, Pa., by many experiments. 

MALLEABLE IRON. 

The manner of converting iron ore into malleable 
iron has undergone many changes since the seventh 
descendant from Adam. Tubal Cain was an " in- 
structor of every artificer in brass and iron." It is 
made from the pig, in the bloomery fire, or in the 
puddling furnace — generally the latter. The process 
consists in melting the pig metal in a reverberatory 
furnace, where the flame is made to act directly on 
the metal, keeping it exposed to a great heat, and con- 
stantly stirring the mass, bringing every part of it 
evenly under the action of the flame, until it loses its 
remaining carbon. It then loses its fluidity, and is 
formed into a puddler's ball, weighing from 80 to 100 
pounds. This is the point or connecting link between 
cast and malleable iron. 

The operation of puddling is a most important one, 



MALLEABLE IEOTf. 199 

as the quality of the iron depends so much upon the 
skill with which it is conducted. After the puddler's 
ball has been formed, it is passed to a heavy strong 
squeezer, or steam hammer, most frequently the former. 
Its object is to press out, as perfectly as possible, the 
liquid cinder which the ball still contains; it also 
forms the ball into shape. It is now called a bloom, 
and is ready to be rolled or hammered — while yet hot 
it is generally passed between the rolls several times, 
and drawn into a bar about five inches wide and three 
quarters of an inch thick; this is called muck bar. 
The next thing is to refine it. To prepare bars for 
this operation, they are cut by a strong pair of shears 
into such lengths as are best adapted to the size of bar 
or sheet required. The sheared bars are then piled 
one on the other, according to the quantity of metal 
necessary to make the finished piece. They are then 
brought to a welding heat, in the heating furnace, and 
passed between the finishing rolls successively until 
drawn to the proper dimensions. For heavy plates, 
and many other forms, pieces called tops and bottoms 
are first rolled some three by two feet and about an 
inch thick, and the before named bars piled — breaking 
joints — between them. Sometimes these tops and 
bottoms are of good stock and the pile very inferior ; 
the result is a poor quality. For better material, the 
iron is double refined ; i. <?., the rough, or muck bar, as 
it is called, being cut to proper lengths, is piled, heated 
as before, rolled into bars, and again piled, heated, and 
rolled to the required dimensions. Another, and we 
consider the better process, is to hammer the heated 
pile into a slab of say 18 by 12 inches and inches 
thick, heat this slab, rehammer it, then roll it to de- 



200 MALLEABLE IEOK. 

sired dimensions. By reheating, hammering or rolling, 
other things being equal, the iron is improved up to 
some five or six workings, after which, further heating 
causes deterioration. 

The quality depends on the kind of pig used, 
the skill of the puddler, and the absence of tleleteri- 
ous substances in the furnace. For the best sheets, 
bars, and for converting into steel, charcoal iron is 
used exclusively, and it can be relied upon for 
strength and toughness with greater confidence than 
any other. 

Bloomery. — This resembles a large forge fire, and 
in it are made the charcoal blooms from which the 
best qualities of all iron and steel are manufactured. 
The pig metal, after being broken into pieces of the 
proper size, is placed before a strong blast directly in 
contact with charcoal ; as the metal fuses it falls into 
a cavity left for the purpose below the blast, when the 
bloomer works it into the shape of a ball, which he 
places again before the blast surrounded with fresh 
charcoal ; after repeating this, the ball is ready for 
and put »under the hammer and hammered into a 
bloom. The bloom is then removed to the reverbera- 
tory furnace, and heated with bituminous coal, to a 
welding heat, then again hammered into a slab, or 
rolled into rough bar. If the former, it is again heated 
and rolled as required. If the latter, it is cut, piled, 
and re-rolled into bar — then treated as before explained. 
Flange boiler plate is made according to both opera- 
tions, and there is a difference of opinion among iron 
masters regarding which process produces the best 
quality. 

Cold Short is the term given to iron that will not 



MALLEABLE IRON. 201 

stand working cold, bending, twisting, or punching 
very near edges, &c. 

Hot Short is iron that will not work advantageously 
hot, but is strong when cold. Both kinds are suitable 
for special purposes, but for machinery neutral iron is 
the kind to be relied upon. By neutral is meant iron 
that can be worked either cold or hot — at all ordinary 
temperatures. 

Forging. — Good iron is often injured by being un- 
skilfully worked. Care should be taken that the iron 
while heating is not exposed to the air. Iron heated 
for any purpose, especially for welding, should be 
heated as rapidly as possible, in order to expose it the 
least possible time to the action of the air and coal ; 
for this purpose, the strongest fuel with an abundant 
steady blast is necessary. 

Bessemer* 8 Patent Process for making Malleable 
Iron. — We have seen that the principal impurities in 
cast iron consist of carbon, sulphur, phosphorus, silicon, 
&c. These substances, Mr. Bessemer asserts, combine 
with the oxygen of the atmosphere at high tempera- 
tures ; he therefore runs the metal from the smelting 
furnace into a close vessel ; when this vessel is about 
half full, numerous small jets of atmospheric air are 
forced in among the fluid metal, and in sufficient quan- 
tities to produce a vivid combustion among the par- 
ticles of the fluid metal. By this process an intense 
heat is generated without the application of any fuel, 
and the labor and expense of puddling are saved. The 
process has been progressing in England for several 
years, and at this date — 1862 — a number of iron mas- 
ters are experimenting with it in this country. If suc- 
cessful, a cheaper and wider field will be open to the 



202 CAST STEEL. 

manufacturers of iron. One of the difficulties Mr. Bes- 
semer has to contend with, is to obtain any kind of 
material that will stand the intense heat. 

PUDDLED STEEL. 

If, in the operation of puddling, the process be 
stopped at a particular time, determined by indications 
given by the metal to an experienced eye, an iron is 
obtained of greater hardness and strength than ordi- 
nary iron, to which the name of semi-steel, or puddled 
steel, has been applied. Chemicals are also used in 
some such furnaces. 

STEEL. 

Steel is a compound of iron and carbon, in which 
the proportion of the latter is from five to one per 
cent, and even less in some kinds. Steel may be dis- 
tinguished from iron by its fine grain, and its suscepti- 
bility of hardening by immersing it, when hot, in cold 
water. 

There are many varieties of steel, the principal of 
which are Mistered steel, shea?' steel, and cast steel. 

Blistered Steel \§ prepared by the direct combination 
of iron and carbon. The process is to take the best 
bars and plates of wrought iron and expose them in a 
converting furnace, for seven or eight days, to a me- 
dium temperature, in contact with powdered charcoal, 
so as to totally exclude the air. The bars, on being 
taken out, exhibit in the fracture a uniform crystalline 
appearance. The degree of carbonization is varied 
according to the purpose for which the steel is in- 
tended. 



CAST STEEL. 203 

Shear Steel is generally made from blistered steel 
refined by piling into fagots, which are brought to a 
welding heat in a reverberatory furnace, hammered 
and rolled again into bars ; this operation is repeated 
several times to produce the finest kind of shear steel. 
The name is derived from the fact that this variety of 
steel was used in England for shears. 

Cast Steel. — For this important invention we are 
indebted to Benjamin Huntsman, of the village of 
Handsworth, near Sheffield, England, who, about the 
year 1740, perfected his invention, from which the 
civilized world has derived such vast and varied ad- 
vantages. It is made by breaking Mistered steel or 
cutting bar iron into small pieces, and melting it in 
combination with a small quantity of charcoal (when 
it is made from iron, manganese is mixed with it) in 
close air-tight crucibles, from which it is poured into 
iron moulds ; the ingot is then reduced to a bar by 
hammering or rolling, as described under the head of 
malleable iron. 

Cast steel is the finest kind of steel. It is known 
by a very fine, even, and close grain, and a silvery and 
homogeneous fracture ; it is very brittle, and acquires 
extreme hardness, but is difficult to weld without the 
use of a flux. The other kinds of steel have a similar 
appearance to cast steel, but the grain is coarser and 
less homogeneous; they are softer, less brittle, and 
weld more readily. 

Properties of Steel. — The best steel possesses the fol- 
lowing characteristics : Heated to redness and plunged 
into cold water, it becomes hard enough to scratch 
glass and to resist the best files ; the hardness is uni- 
form throughout the piece ; after being tempered it is 



204 CAST STEEL. 

not easily broken ; it welds readily ; it does not crack 
or split; it bears a very high heat, and preserves the 
capability of hardening after repeated working ; the 
grain is fine, even, and homogeneous, and it receives a 
brilliant polish. 

Hardening and Tempering, — On these operations 
the quality of manufactured steel in a great measure 
depends. 

Hardening is effected by heating the steel to 
cherry red and plunging it into a liquid, generally cold 
water; the degree of hardness depends on the heat 
and rapidity of cooling. 

Tempering. — Steel in its hardest state being too 
brittle for most purposes, the requisite strength and 
elasticity are obtained by tempering, which is per- 
formed by heating the hardened steel to a certain 
degree and cooling it quickly. The requisite heat is 
usually ascertained by the color which the surface of 
the steel assumes — a straw color is common for cold 
chisels and machinists' tools. 

Case Hardening. — This operation consists in con- 
verting the surface of wrought iron into steel, by heat- 
ing the iron to a cherry red, in a close vessel, in contact 
with carbonaceous materials, and then plunging it into 
cold water. Bones, leather, hoofs, and horns of animals 
are used for this purpose, after having been burnt or 
roasted, and pulverized. Soot is also frequently used. 

To Test the Quality of Boiler Iron. — Bend it cold 
at sharp angles, and double the pieces together ; heat 
it cherry red, and perform the same operation, and 
punch holes very near the edges of the sheets. If it 
stands these tests without cracking, it is neutral iron, 
and of the best quality. 



CAST STEEL. 205 

To Test the Quality of Bar Iron. — Cut a notch on 
one side with a cold chisel, then bend the bar over 
the edge of an anvil at sharp angles. If the fracture 
exhibits long silky fibres, of a leaden gray color, co- 
hering together, and twisting or pulling apart before 
breaking, it denotes tough, soft iron, easy to work and 
hard to break. In general, a short, blackish fibre in- 
dicates iron badly refined. A very fine close grain 
denotes a hard steely iron, which is apt to be cold 
short, but working easily when heated, and making a 
good weld. Numerous cracks on the edges of the bar 
generally indicate a hot short iron, which cracks or 
breaks when punched or worked at a red heat, and 
will not weld. Blisters, flaws, and cinder holes are 
caused by imperfect welding at a low heat, or by iron 
not being properly worked, and do not always indicate 
inferior quality. 

To Test Iron tvhen Hot — Draw a piece out, bend 
and twist it, split it and turn back the two parts, to 
see if the split extends up ; finally, weld it, and observe 
if cracks or flaws weld easily. Good iron is frequently 
injured by being unskilfully worked: defects caused 
by this may be in part remedied. If, for example, it 
has been injured by cold hammering, moderate anneal- 
ing heat will restore it. 

Steel. — To test steel, break a few bars, taken at 
random, make tools of them, and try them in the 
severest manner. 

For further information on the subject of materials, 
we refer the reader to an excellent work called " Use- 
ful Metals and their Alloys," by Messrs. Clay, Aitken, 
Vospicket, and Fairbairn. 



206 



TENACITY OF MATERIALS. 



Tenacity of Materials. 



Bar-iron 



Cast-iron 



Specimens from gun heads. 



Cast Steel .... 134,000 lbs, 

Swedish 72,000 

Salisbury, Conn 66,000 

Belleionte, Pa 58,500 

English 56,000 

[Pittsfield, Mass... 57,000 

fPig metal 15,000 

Good common castings 20,000 

24,000 
39,500 
,128,000 
30,000 
42,000 

Copper, cast, (Lake Superior) 24,138 J 

Brass * 18,000 

n S Wrought 34,000 

C °PP er \ Cast..!. 19,000 

Tin, cast 4,800 

Zinc 3,500 

Platinum 56,000 

Silver 40,000 

Gold 30,000 

Lead 1,800 



Cast Steel. 

Bronze — sun metal. 



Experiments by Frank- 
lin Institute, on bars 
"whose cross section 
was about one-fifth 
of a square inch. 

Experiments of Maj. W. 
Wade, for the Ord- 
nance Department, 
on pieces whose cross 
section was nearly 1 
square inch. 



Ash 15,800 

Mahogany 11,500 

Oak 11,600 

White Pine 11,800 

Walnut 7,700 

In general, the tenacity of metals is increased by 
hammering and wiredrawing. The strength of Pitts- 
field bar iron, given in the above table, is the mean of 
fonr trials, with cylinders 1 inch long and 0.9 inch di- 
ameter. They w r ere extended in length, before frac- 
ture, to 1.4 in., and they were reduced in diameter to 
0.6 in. in the middle. 

A bar of wrought iron is extended about one-hun- 
dredth part of its length for every ton of strain on a 
square inch. 

Transverse Strength 

S = the weight in pounds required to break abeam 
1 in. square and 1 in. long, fixed at one end and loaded 
at the other ; b the breadth, d the depth, and I the 



RESISTANCE TO TORSION. 207 

length, in inches, of any other beam of the same mate- 
rial, and W the weight which will cause it to break, 
neglecting the weight of the beam itself. 

1. If the beam is supported at one end, and loaded at the other : 

W = B T 

2. If the beam is supported at one end, and the load distributed over its 
whole length : 

W=2S T 

8. If the beam is supported at both ends, and loaded in the middle : 

W = 4S T 

4. If the beam is supported at both ends, and loaded uniformly over its 

whole length : 

bd* 
W = 8S- r 

5. If the beam is supported at both ends, and loaded at the distance m from 
one end : 

W = S -77 c 



Resistance to Tor 



81071. 



S = the weight in pounds required to break, by 
twisting, a solid cylinder, 1 inch diameter ; the weight 
acting at the distance of 1 inch from the axis of the 
cylinder ; d, the diameter in inches of any other cylin- 
der of the same material ; r, the distance from its axis 
to the point where the breaking weight W is applied ; 
then : 



w = s 7 



Results of Repeated Heating Bar Iron. 

In a series of experiments, with regard to the im- 
provements and deterioration which result from oft- 
repeated heating and laminating of bar iron, made by 
William Clay, Esq., of the Mersey steel and iron works, 
Liverpool, he says that, taking a quantity of ordinary 
14 



208 RESULTS OF EEPEATED HEATING BAR IKON. 

fibrous puddled iron, and reserving samples marked 
No. 1, we piled a portion live high, heated and rolled 
the remainder into bars marked No. 2, again reserving 
two samples from the centres of these bars, the remain- 
der were piled as before, and so continued until a por- 
tion of the iron had undergone twelve workings. 

u The following table shows the tensile strain which 
each number bore : 

No. Pounds. 

1. Puddled bar 43,904 

2. Re-heated 52,864 

3. " 59,585 

4. " 59,585 

5. " 57,344 

6. " 61,824 

7. " 59,585 

8. " 57,344 

9. " 57,344 

10. " 54,104 

11. " 51,968 

12. " . 43,904 

" It will thus be seen that the quality of the iron 
increased up to No. 6, (the slight difference of No. 5 
may, perhaps, be attributed to the sample being slightly 
defective)'; and that from No. 6 the descent was in a 
similar ratio to the previous increase." 

TENSILE STRENGTH OF IRON AND STEEL BARS PER SQUARE INCH. 



Description of Iron and Steel. 



Russian Iron 

English Rolled Iron.... 

Lawmoor " 

American Hammered. 



Krupp's Cast Steel, average of 3 samples... 
Cast Steel, highest 

14 mean 

<t « 

" tempered 

Shear Steel , 

Blister " 



Mersey Steel and Iron Co. Puddled steel, 

highest 

Dito, another sample 

Average of three samples tested at the Liv- 
erpool Corporation testing machine 



Tensile Strength. 



62,644 
56,532 
56,103 
53,913 



111,707 
142,222 
88,657 
134,256 
150,000 
124,400 
133,152 



173,817 
160,832 

112,000 



Authority. 



American Board of 
Ordnance, 



Min. of War, Berlin. 

Mallett. 

do. 



STRENGTH OP JOINTS OF BOILER PLATES. 209 



On the strength of the joints of single and double riveted 
boiler plates, by William Fairbaim, Esq., F. R. S. 

On comparing the strength of plates with their 
riveted joints, it will be necessary to examine the sec- 
tional areas taken in a line through the rivet-holes with 
the section of the plates themselves. It is perfectly 
obvious, that in perforating a line of holes along the 
edge of a plate, we must reduce its strength : it is also 
clear that the plate so perforated will be to the plate 
itself, nearly as the areas of their respective sections, 
with a small deduction for the irregularities of the 
pressure of the rivets upon the plate ; or, in other 
words, the joint will be reduced in strength somewhat 
more than in the ratio of its section through that line 
to the solid section of the plate. It is evident that the 
rivets cannot add to the strength of the plates, their ob- 
ject being to keep the two surfaces of the lap in contact. 

When this great deterioration of strength at the 
joint is taken into account, it cannot but be of the 
greatest importance that in structures subjected to such 
violent strains as boilers and ships, the strongest 
method of riveting should be adopted. To ascertain 
this, a long series of experiments 
were undertaken by Mr. Fairbairn, 
some of the results of which will 
be of interest here. The joint or- 
dinarily employed in ship building 
is the lap joint, shown in Figs. 1 
and 2. The plates to be united 
are made to overlap, and the rivets 
are passed through them, no cov- 
ering-plates being required, except 
at the ends of the plate, where they butt against each 



Fi 3 .l 


~) 


9 Q> o 9 e o el a \ 
Fig.Z. 


03(3(5 90 



<> 



210 STRENGTH OF JOINTS OP BOILER PLATES. 

other. It is also a common practice to countersink the 
rivet-heads on the exterior of the vessel, that the hull 
may present a smooth surface for her passage through 
the water. This system of riveting is only used when 
smooth surfaces are required; under other circum- 
stances, their introduction would not be desirable, as 
they do not add to the strength of the joint, but, to a 
certain extent, reduce it. There are two kinds of lap- 
joints, those said to be single-riveted (Fig. 1), and those 
which are double-riveted (Fig. 2). At first, the former 
were almost universally employed, but the greater 
strength of the latter has since led to their general 
adoption in the larger descriptions of vessels. The rea- 
son of the superiority is evident. A riveted joint gives 
way either by shearing off the rivets in the middle of 
their length, or by tearing through one of the plates 
in the line of the rivets. In a perfect joint, the rivets 
should be on the point of shearing just as the plates 
were about to tear ; but in practice, the rivets are 
usually made slightly too strong. Hence, it is an estab- 
lished rule, to employ a certain number of rivets per 
lineal foot. If these are placed in a single row, the 
rivet-holes so nearly approach each other, that the 
strength of the plates is much reduced ; but if they 
are arranged in two lines, a greater number may be 
used, and yet more space left between the holes, and 
greater strength and stiffness imparted to the plates at 
the joint. 

The experiments of Mr. Fairbairn and others have 
established the following relative strengths as the 
value of plates with their riveted joints : 

Taking the strength of the plate at 100 

The strength of the double-riveted joint would then be 70 

And the strength of the single-riveted joint. ...« ........ 5ft 



MOTION. 211 



THE ELEMENTS OF MACHINERY. 

In consequence of having found many young en- 
gineers unacquainted with the principles of mechani- 
cal powers, we have thought best to devote a short 
space to the subject, prefacing it with the description 
of motion, and application of power, by David A. 
Wells, A. M. 

Motion, 

Motion is the act of changing place. It is absolute 
or relative. Absolute motion is a change of position 
in space, considered without reference to any other 
body. Kelative motion is motion considered in rela- 
tion to some other body, which is either in motion or 
at rest. 

"When a body commences to move from a state 
of rest, there must be some force to cause its motion, 
and this force is generally termed " Power." On the 
contrary, a force acting to retard a moving body, de- 
stroy its motion, or drive it in a contrary direction, 
is termed " Kesistance." The chief causes which tend 
to retard or destroy the motion of a body are gravi- 
tation, friction, and resistance of the air. 

The speed, or rate, at which a body moves, is 
termed velocity. The momentum of a body is its 
quantity of motion, and this expresses the force with 
which one body in motion would strike against 
another. This momentum, or force, which a moving 
body exerts, is estimated by multiplying its weight 
by its velocity. Thus a body weighing 20 lbs., and 
moving with a velocity of 200 feet per second, will 
have a momentum of 20 X 200 = 4000. 



212 APPLICATION OF POWEB. 

Action and Reaction. 
When a body communicates motion to another 
body, it loses as much of its own momentum, or force, 
as it gives to the other body. The term Action is 
applied to designate the power which a body in mo- 
tion has to impart motion, or force, to another body ; 
and the term Reaction to express the power which 
the body acted upon has of depriving the acting body 
of its force or motion. There is no motion, or action 
without a corresponding and opposite action of equal 
amount ; or, in other words, action and reaction are 
always equal and opposed to each other. 

Application of Power. 

The principal agents from whence we obtain 
power for practical purposes, are men and animals, 
water, wind, steam, and gunpowder. 

When work is performed by any agent, there is 
always a certain weight moved over a certain space, 
or resistance overcome ; the amount of work per- 
formed, therefore, will depend on the weight, or re- 
sistance that is moved, and the space over which it is 
moved. For comparing different quantities of work 
done by any force, it is necessary to have some stand- 
ard ; and this standard is the power, or labor, ex- 
pended in raising a pound weight one foot high, in 
opposition to gravity. 

A machine is an instrument, or apparatus, adapted 
to receive, distribute, and apply motion derived from 
some external force in such a way as to produce a 
desired result ; but it cannot, under any conditions, 
create power, or increase the quantity of power or 
force applied to it. Perpetual motion, or the con- 
struction of machines which shall produce power 
sufficient to keep themselves in motion continually, is, 



APPLICATION OF POWER. 213 

therefore, an impossibility, since no combination of ma- 
chinery can create, or increase, the quantity of power 
applied, or even preserve it without diminution. 

The great general advantage that we obtain from 
machinery is, that it enables us to exchange time and 
space for power. Thus, if a man could raise to a cer- 
tain height 200 pounds in one minute, with the 
utmost exertion of his strength, no arrangement of 
machinery could enable him unaided to raise 2000 
pounds in the same time. If he desired to elevate 
this weight, he would be obliged to divide it into ten 
equal parts, and raise each part separately, consuming 
ten times the time required for lifting 200 pounds. 
The application of machinery would enable him to 
raise the whole mass at once, but would not decrease 
the time occupied in doing it, which would still be 
ten minutes* 

The power will overcome the resistance of the 
weight, and motion will take place in a machine, 
when the product arising from the power multiplied 
by the space through which it moves in a vertical 
direction, is greater than the product arising from 
the weight multiplied by the space through which it 
moves in a vertical direction. Thus if a small power 
acts against a great resistance, the motion of the lat- 
ter will be just as much slower than that of the 
power, as the resistance or weight is greater than the 
power, or if one pound be required to overcome the 
resistance of two pounds, the one pound must move 
over two feet in the same time that the resistance, 
two pounds, requires to move over one. 

All machines, no matter how complex and intri- 
cate their construction, may be reduced to one or 
more of six simple machines, or elements, which we 
call the 



214 THE LEVER. 

Mechanical Powers. 

The simple machines, six in number, are usually 
denominated the lever, inclined plane, wheel and 
axle, pulley, screw, and wedge. 

The wheel and axle is, however, a revolving lever, 
the screw a revolving inclined plane, and the wedge 
a double inclined plane, thus reducing them to three 
in number, viz. : lever, inclined plane, and pulley. 

All these machines act on the same fundamental 
principle of virtual velocities ; accordingly, the weight 
multiplied into the space it moves through is equal to 
the power multiplied into the space it moves through. 
This is the general law which determines the equi- 
librium of all machines ; and keeping this principle 
in mind, there will be no difficulty in solving any of 
the propositions appertaining to the simple machines. 

In all machines, a portion of the effect is lost in 
overcoming the friction of the working parts; but, 
in making calculations upon them, it is made first as 
though no friction existed, a deduction being after- 
wards made. And so also we have to assume a per- 
fection in the machine itself which does not exist ; 
that is to say, the inclined plane, screw, wedge, &c, 
to be a perfectly smooth hard inflexible substance, 
and the rope of the pulley, and wheel and axle, to be 
perfectly flexible and non-elastic, conditions, for which 
allowance has to be made after the calculation is 
completed. 

Lever. — Of the lever there are three orders, as 
shown respectively by the figures 1, 2, 3. 

Hgf. ± 



± 




X 



7\ 




THE LEVEE. 



215 




Fig. 3 



< i 



W = weight, P == power, F = fulcrum. 

Example 1.— Given the Weight W == 1000 lbs., 
required the power P, the lengths of the arms re- 
spectively as marked in the figures ? 

Ans. 1.— P x 3 = 1000 X 1 
3P = 1000 
P = 3331- lbs. 



Ans. 


2.- 


-P 


X4 = 

4P = 
P = 


1000 X 1 
1000 
: 250 lbs. 


Aks. 


3.- 


-P 


Xl = 
P = 


1000 X 4 
4000 lbs. 



Example 2. — Given a compound lever with lengths 



4: X 




J6 



-p Tig". 4. 



< 2 X 



^ 



4k\ 

and weight as marked in fig. 4, required the power P. 



216 THE LEVEE. 

p X 16 = 1000 X 4 
16j9 = 4000 
p==250 lbs. == weight required at 
p, supposing there to be but one lever — therefore 

P x 10 = 250 X 2 
10P = 500 
P = 50 lbs. 



Or, 



1000 x4x2 = Pxl0xl6 
8000 == 160P 
P= 50 



Example 3. — Given, as per figure 5, a safety valve 



Tig", 5 

5 X 20 



A 



ITT 



100 sqr. ins. area 

20 lbs. per sq. in. pressure 
2000 lbs. total pressure. 

100 sq. ins. area, subject to a pressure per square inch 
above the atmosphere of 20 lbs., lengths of the long 
and short arms of the lever as shown in the figure, 
required the weight W to balance the pressure on the 
valve ? 

Wx 25 = 100 X 20 X 5 
25W = 10000 
W = 400 lbs. 

Example 4. — Suppose, in example 3, the valve and 
stem should weigh 20 lbs., and the lever, which is 
uniform throughout its length, weigh 2.5 lbs., what 
would be the weight W, in that case, to balance the 
same pressure of steam ? 

The valve and stem being 5 inches from the ful- 
crum, act with a leverage of 5 inches, but the lever 
being uniform, its action is the same as though the 



INCLINED PLANE. 



217 



whole weight was concentrated at x (the centre of 
gravity) half way of its length. "Wherefore 

W X 25 + 20 X 5 + 25 X 12.5 = 100 X 20 X 5 
25W + 100 + 312.5 = 10000 

25 W = 10000 -412.5 
W = 383.5 lbs. the re- 
quired weight. 

Practically, the pressure a safety valve lever ex- 
erts on the valve can be ascertained by fixing it in its 
place, and attaching a spring balance to the pin hole 
immediately over the valve. If the valve and weight 
be also attached, the balance will indicate the total 
pressure which tends to keep the valve in its seat, 
which pressure being divided by the number of square 
inches in the valve, will give the pressure per square 
inch at which steam will commence to blow off. 



JTig. 6. 




Inclined Plane. 
Ex. 1.— Weight W 500 lbs., 
length, and height of the plane, 
as per figure 6, 20 and 9 ins. 
respectively, required the pow- 
er P? 

Considering the weight W to be started at the 
base of the plane and rolled up to the top, it will 
travel vertically the height of the plane, (9 inches), 
while the power, P, will descend a distance equal to 
the length of the plane (20 ins.), therefore, according 
to the principle of virtual velocities, 

P X 20 = 500 X 9 
, 20P = 4500 

! P = 225 lbs. 




)2» Ex. 2. — Length and 
height of the plane as 
per iig. 7, weight 500 
pounds, required the 



218 



INCLIKED PLANE. 



power P applied in a line with the base of the 
plane ? 

In this case, when the weight will have risen from 
the base to the top of the plane, 9 ins., the distance 
descended by P will manifestly not be equal to the 
length but to the base. Wherefore 



Px 



v/20 2 -9 3 =500 X 9 
17.86P = 4500 

P = 251.96 - lbs. 




In order to establish Equilibrium between the 
weight and power, this calculation is also applicable 

when the power is 
applied in the di- 
rection of the base 
as shown in dots, 
figure 7. 

If the power be 
applied at an angle 
with the plane, as 
jd 1 C A, figure 8, in 

order to ascertain the proportion of weight to the 
power, to establish equilibrium, we proceed thus : 
Draw CD, the vertical of the centre of gravity of the 
weight, of any convenient length ; CE, at right angles 
to BF, and DE parallel to AC. CD can represent 
the length of the plane, and DE the height. Where- 
fore 

Weight xDE = Power x CD 
Power = Weight x DE 
CD 
Geometrically, the angles B#C and CDE, from 
the construction of the figure, can be demonstrated 
to be equal, and also ECD, and BFGr ; from which, 
knowing the lengths of two legs of the triangle BFG, 



WHEEL AND AXLE. 



219 



and the angle G, to be a right angle, the lengths of 
the lines CD ED can be determined. 



Wheel and Axle. — In the wheel and axle, when 
the power is applied tangentially to the wheel, 

W X radius of axle = P x radius of wheel 
W X diameter of axle = Px diameter of wheel 
W X circumference of axle = P x circum. of wheel. 

When the power is not applied 
tangentially to the wheel, but in the 
direction shown in Hg. 9, the length 
of the line ab at right angles to the 
power will give the leverage of the 
power, — hence 



W x radius of axle =Px«5. 




Tig. 9. 



TT 



Pulley.— If. a cord be pulled at one end the ten- 
sion throughout its whole length must be alike. 
Taking figure 10, and supposing the power to be 1, 
the tension throughout the entire 
length of the cord will be 1, but 
as there are two parts of the cord 
supporting the lower block, the 
weight must be 2. The pressure 
on the fulcrum or support must 
be always equal to the weight, 
plus the power. If there be 
more than one support, the sum 
of the pressures on them will be 
equal to the sum of the weight 
and power. Or, in figure 10, 
according to the principle of virtual velocities, the 
weight is double the power, because the power must 
descend 2 feet for every foot ascent of the weight. 




Fig-. 10 



220 



THE PULLEY. 



The numbers above the top blocks in all the ex- 
amples of pulleys here shown represent the pressure 
on the supports. 

In fig. 11, the power and weight are as 1 to 8, because 
the power supports 4 weights, each one double its size. 



JElg\U 




In fig. 12 the tension 
on the 1st cord is 1 ; on 
the 2d 2 ; 3d 4 ; 4th 8 ; 
5th 16 ; and as there are 
2 parts of the cord hav- 
ing a tension of 16, the 
weight to establish equi- 
librium, must be 32. 

In%. 13 the weight 
to the power is as 3 to 
1, there being 3 parts 
of the cord having a 
tension of 1 supporting 
the weight. 



Hg;13 




THE PULLEY. 



221 



In %. 14 the power 
to the weight is as 1 
to 12, the power being 
multiplied four times 
by the application of 
the second set of pul- 
leys, or luff-tackles, 
as they are technically 
termed. 

In fig. 15 the power 
is to the weight as 
1 to 12, the tension 
throughout the first 
cord being 1 ; the sec- 
ond cord 2 ; third 5, 
and as there are two 
parts of the cord hav- 
ing a tension of 5, and 
one part of the cord 
having a tension of 2, 
supporting the weight, 
if all the cords be 
supposed parallel, the 
weight must be the 
sum of these, or 12. 

In fig. 16 the power 
to the weight is as 1 
to 4. 

In figure 17, where 
the power is applied 
at an angle, we ascer- 
tain the proportion of 
the weight and power 
thus: Draw AD, of 
any convenient length 
and from the point A 
draw AB parallel to 



Tig. 14, 




Hg\;15i 



222 



THE PULLEY, 




Cc and AC parallel to BS. The 
power and weight will be re- 
spectively as the lengths of the 
lines DC or DB and AD. 



3?ig.l6 




JFig\±7. 



From which it will be seen that the greater the 
angle CDB the longer will be the line DC or DB, and 
hence the greater the power. So that the weight of the 
line itself will be sufficient to prevent any power 
whatever from drawing it mathematically straight. 



vr 




Question.— In figure 18, two blocks of granite, 
joined together as shown, are laid upon a horizontal 
plane ; required their relative sizes in order that they 
may commence at the same time to move, and con- 
tinue to move with equal velocity ? 

Am — 2 to 1, because the larger block is supported 
by two parts of the cord, and has in consequence, 
double the force exerted upon it of the smaller block. 



THE SCREW. 



223 



D 



20 



l~l Eig;ie 



> Scretv. — In the screw, 
T like all other simple ma- 
chines the power X space 
moved through = weight 
X space moved through. 
Ex. — Length of lever 
20 ins., pitch of screw \ 
inch, weight 500 lbs., re- 
quired the power P at 
the end of the lever ? 
Ans. Px 20x2x3.1416 
= 500 X T 
125.664P == 250 

P == 1.989 lbs. 



20 



Tig. 20 



JD 




The screw is simply a 
revolving inclined plane, 
the power being applied 
parallel to the base of 
the plane, which is repre- 
sented by the circumfer- 
ence described by P, and 
the height of the plane 
by the pitch of the screw. 

Fig. 20 is a compound 
screw. The upper screw 
AA is fitted to the thread 
in the nut B which re- 
mains fixed. The cylin- 
der AA being hollow has 
another screw C, of a finer 
thread, fitting into it. 
The nut D is fixed, al- 
lowing C to slide up and 
down within it, without 



224 



THE WEDGE. 



turning. By this arrangement it will be seen, that 
when the screw AA is turned once round, the distance 
ascended "by the weight will not be equal to the pitch 
of AA, but the difference between the pitch of AA 
and C. 

Example. — Pitch of AA \ inch, of C T 7 T inch, 
weight 16000 lbs., required the power P, applied 20 
inches from the centre ? 



16000 X T V 



Ans.— P x 20 X 2 X 3.1416 

125.664P = 1000 

P = 7.957 lbs 



In order to multiply the power the same number 
of times with a single screw, the pitch would have to 
be T ! g- inch, which would render the thread too weak 
to withstand a heavy pressure. 

Wedge.— Let WW, 

fig. 21, be two weights 
of 1000 lbs. each, rest- 
ing upon a horizontal 
-t?'^ of plane, required the 
power to be applied 
at P, to the wedge, 
having the dimensions 
shown in the fisrure to 
"*" to separate them ? 

P X 20 = 1000 X 2 
20P == 2000 
P = 100 lbs. 

Because, when the power P has descended to the 
point A, the weights have been separated 2 inches 
while the power has travelled 20 inches, the length 
of the wedge. 



i 

1 


*4 

I 


r 


w 

_. \ 




| ^ 



GRAVITY. 



225 



Centre of Gravity. 

The centre of gravity of a cone from the vertex 
equals f- the axis. 

In a paraboloid, the distance from vertex equals f 
the axis. 

In a parabolic space, equals f the axis from the 
vertex. 

In a triangle, equals -§ the axis from the vertex. 



Centre of Pressure. 

The centre of pressure of a parallelogram, when 
the upper surface is level with the water, = \ from the 
bottom ; of a right-angled triangle with 
the base down = \ from the bottom, 
measured on the perpendicular line 
B C ; with the base up = \ B C. — See 
Hariri! s Mechanics. 




Semi-parabolic plane. 



formula : 
m = centre of pressure, 



b m= \ of a <?, 
mn = yV of a d. 



Gravity. 

The spaces described by a body acted upon freely 
by gravity are as the squares of the times ; i. e., a body 
falling 2 seconds, will describe 4 times the distance of 



226 GKAVITY. 

a body falling one second. Hence, in order to ascer- 
tain the distance fallen by a body, it is only necessary 
to multiply the square of the number of seconds by 
the distance fallen in the first second ; the product will 
be the total distance fallen. 

All bodies fall with the same velocity in vacuo, 
namely, 16.08 feet in the first second, having a velocity 
of 32.166 feet at the end of the second. Where the 
atmosphere is interposed, the velocity will be some- 
what less, say for heavy bodies, such as the metals, 16 
feet for the first second. 

Example. — Which will strike with the greater 
effect, a weight of 200 lbs., falling through 144 ft., or 
100 lbs. falling through 256 feet ? 

The velocity of a body at the end of a fall is equal 
to the number of seconds it is falling, multiplied into 
(32 feet) the velocity at the end of the first second, 
and the momentum of a body is equal to the weight 
multiplied into the velocity. We have, then, first to 
find the velocity, and afterwards the momentum. 

y/W : 1 : : Vl4A : 3 seconds time of falling of 200 lb. 

VT6: 1 :: ^256:4 " " " 100 lb. 

32 X 3 = 96 ft. per second velocity at end of fall 

of 200 lb. weight. 
32 X 4 = 128 ft. per second velocity at end of fall 

of 100 lb. weight. 
96X200=19200= momentum of the 200 lb. weight. 
128x100=12800= momentum of the 100 lb. weight. 
6400= difference, which is 33| per cent* 
of the larger number. 



DISPLACEMENT OF FLUIDS. 227 

Centre of Gravity of Several Bodies taken together. 

Suppose there be several weights placed as follows 
in the same plane, required the centre of gravity of 
them all taken together ? 



Cylinder. 
Tone. 




Air-pump. 
Tone. 


Shaft. 
Tons. 


Boilers. 
Tons. 


5 




2 


10 


30 


< 


8 ft. 


X 10 ft 


X 20 ft. 


> 



a 

Assume a point (#), at any distance (say 2 feet) 
from either of the extreme weights, and multiply each 
weight separately by its distance from this point ; the 
sum of these products, divided by the sum of the 
weights, will be the distance of the centre of gravity 
from the assumed point. Thus : 

30 X 2 = 60 
10 X 22 = 220 

2 x 32 = 64 

5 x 40 = 200 



47 ) 544 (11.57 ft. = centre of 

gravity from the point a, or 9.57 feet from the boilers 
towards the shaft. 

Displacement of Fluids. 

Solid bodies immersed in fluids will displace an 
amount of the fluid equal to their own weight. If the 
specific gravity of the body be greater than that of 
the fluid, it will sink ; otherwise it will float. 

Example. — Kequired the distance a cube of cherry, 
one foot high, will sink in fresh water ? 

The specific gravities of fresh water and cherry are 
relatively as 1.00 to .606 ; the cherry will therefore 
sink .606 feet. 



228 EOECE, TEMPEEATEEE, AND VOLUME OE STEAM. 



Table of the Elastic Force, Temperature, and Volume of Steam, from a 
Temperature of 80° to 387.3°, and from a Pressure of one to 410 Inches 
of Mercury. 



Elastic force in 


Tempera- 
ture. 


| 
Yolume. 


Elastic force in 


Tempera- 
ture. 


Yolume. 










inches of 


pounds per 






inches of 


xmnds per 
sq. inch. 






mercury. 


sq. inch. | 






mercury. 






1 


.49 


80 


41031 


53.04 


26 


243.3 


1007 


1.17 


.573 


85 


35393 


55.08 


27 


245.5 


973 


1.36 


.666 


90 


30425 


57.12 


28 


247.6 


941 


1.58 


.774 


95 


26686 


59.16 


29 


249.6 


911 


1.86 


.911 


100 


22873 


61.2 


30 


251.6 


883 


2.04 


1 


103 


20958 


63.24 


31 


253.6 


857 


2.18 


1.068 


105 


19693 


65.28 


32 


255.5 


833 


2.53 


1.24 


110 


16667 


67.32 


33 


257.3 


810 


2.92 


1.431 


115 


14942 


69.36 


34 


259.1 


788 


3.33 


1.632 


120 


13215 


71.4 


35 


260.9 


767 


3.79 


1.857 


125 


11723 


73.44 


36 


262.6 


748 


4.34 


2.129 


130 


10328 


75.48 


37 


264.3 


729 


5 


2.45 


135 


9036 


77.52 


38 


265.9 


712 


5.74 


2.813 


140 


7938 | 


79.56 


39 


267.5 


695 


6.53 


3.1 


145 


7040 ! 


81.6 


40 


269.1 


679 


7.42 


3.636 


150 


6243 j 


83.64 


41 


270.6 


664 


8.4 


4.116 


155 


5559 i 


85.68 


42 


272.1 


649 


9.46 


4.635 


160 


4976 


87.72 


43 


273.6 


635 


10.68 


5.23 


165 


4443 


89.76 


44 


275 


622 


12.13 


5.94 


170 


3943 


91.8 


45 


276.4 


610 


13.62 


6.67 


175 


3838 


93.84 


46 


277.8 


598 


15.15 


7.42 


180 


3208 


95.88 


47 


279.2 


586 


17 


8.33 


185 


2879 


97.92 


48 


280.5 


573 


19 


9.31 


190 


2595 


99.96 


49 


281.9 


564 


21.22 


10.4 


195 


2342 


102 


50 


283.2 


554 


23.64 


11.58 


200 


2118 


104.04 


51 


284.4 


544 


26.13 


12.7 


205 


1932 


106.08 


52 


285.7 


534 


28.84 


14.13 


210 


1763 ! 


108.12 


53 


286.9 


525 


29.41 


14.41 


211 


1730 j 


110.16 


54 


288.1 


516 


30 


14.7 


212 


1700 


112.02 


55 


289.3 


508 


30.6 


15 


212.8 


1669 


j 114.24 


56 


290.5 


500 


31.62 


15.5 


214.5 


1618 


116.28 


57 


291.7 


492 


32.64 


16 


216.3 


1573 


j 118.32 


58 


292.9 


484 


33.66 


16.5 


218 


1530 


1 120.36 


59 


294.2 


477 


34.68 


17 


219.6 


1488 


| 122.4 


60 


295.6 


470 


35.7 


17.5 


221.2 


1440 


i 124.44 


61 


296.9 


463 


36.72 


18 


222.7 


1411 


j 126.48 


62 


298.1 


456 


37.74 


18.5 


224.2 


1377 


128.52 


63 


299.2 


449 


38.76 . 


19 


225.6 


1343 


I 130.56 


64 


300.3 


443 


39.78 


19.5 


227.1 


1312 


132.62 


65 


301.3 


437 


40.80 


20 


228.5 


1281 


134.64 


66 


302.4 


431 


41.82 


20.5 


229.9 


1253 


! 136.68 


67 


303.4 


425 


42.84 


21 


231.2 


1225 


] 138.72 


68 


304.4 


419 


43.86 


21.5 


232.5 


1199 


140.76 


69 


305.4 


414 


44.88 


22 


233.8 


1174 


142.8 


70 


306.4 


408 


45.90 


22.5 


235.1 


1150 


1 144.84 


71 


307.4 


403 


46.92 


23 


236.3 


1127 


1146.88 


72 


308.4 


398 


46.94 


23.5 


237.5 


1105 


148.92 


73 


309.3 


393 


48.96 


24 


238.7 


1084 


150.96 


74 


310.3 


388 


49.98 


24.5 


239.9 


1064 


153.02 


75 


311.2 


383 


51. 


25 


241 


1044 


155.06 


76 


312.2 


379 



FORCE, TEMPERATURE, 



AND VOLUME OF STEAM. 



229 



Elastic force in 


Tempera- 


Volume. 


Elastic force in 


Tempera- 


Volume. 


inches of 


pounds per 


ture. 


inches of 


pounds per 


ture. 


mercury. 


sq. inch. 






mercury. 


sq. in. 






157.1 


77 


313.1 


374 


254.99 


125 


349.1 


240 


159.14 


78 


314 


370 


265.19 


130 


352.1 


233 


161.18 


79 


314.9 


366 


275.39 


135 


355 


224 


163.22 


80 


315.8 


362 


285.59 


140 


357.9 


218 


165.26 


81 


316.7 


358 


295.79 


145 


360.6 


210 


167.3 


82 


317.6 


354 


306 


150 


363.4 


205 


169.34 


83 


318.4 


350 


316.19 


155 


366 


198 


171.38 


84 


319.3 


346 


326.39 


160 


368.7 


193 


173.42 


85 


320.1 


342 


336.59 


165 


371.1 


187 


183.62 


90 


324.3 


325 


346.79 


170 


373.6 


183 


193.82 


95 


328.2 


310 


357 


175 


376 


178 


203.99 


100 


332 


295 


367.2 


180 


378.4 


174 


214.19 


105 


335.8 


282 


377.1 


185 


380.6 


169 


224.39 


110 


339.2 


271 


387.6 


190 


382.9 


166 


234.59 


115 


342.7 


259 


397.8 


195 


384.1 


161 


244.79 


120 


345.8 


251 


408 


200 


387.3 


158 



D. Van JVostrand's .Publications. 

The Political and Military Hiftory 
of the Campaign of Waterloo. 

Translated from the French of General Baron de Jomini. By 
Capt. S. V. Benet, U. S. Ordnance. 1 vol. 12mo, cloth, second 
edition. 75 cents. 

"Baron Jomini has the reputation of being one of the greatest military his- 
torians and critics of the century. His merits have been recognized by the 
highest military authorities in Europe, and were rewarded in a conspicuous 
manner by the greatest military power in Christendom. He learned the art of 
war in the school of experience, the best and only finishing school of the soldier. 
He served with distinction in nearly all the campaigns of Napoleon, and it was 
mainly from the gigantic military operations of this matchless master of the 
art that he was'enabled to discover its true principles, and to ascertain the best 
means of their application in the infinity of combinations which actual war pre- 
sents. Jomini criticizes tbe details of Waterloo with great science, and yet in a 
manner that interests the general reader as well as the professional. 11 — New 
York World. 

"This book by Jomini, though forming the twenty-second chapter of his 
*Life of Napoleon,' is really a unit in itself, and forms a complete summary of 
the campaign. It is an interesting volume, and deserves a place in the affec- 
tions of all who would be accomplished military men." — New York Times. 

"The present volume is the concluding: portion of his great work, 'Vie Poli- 
tique et Militaire de Napoleon, 1 published in 1826. Capt. Benet's translation of 
it has been for some time before tbe public, and has now reached a second edi- 
tion; it is very ably executed, and forms a work which will always bo interest- 
ins, and especially so at a time when military affairs are uppermost in the public 
mind." — Philadelphia North American. 



A Treatife on the Camp and March. 

With which is connected the Construction of Field Works and Mil 
itary Bridges ; with an Appendix of Artillery Ranges, &c. 
For the use of Volunteers and Militia in the United States. 
By Capt. Henry D. Grafton, U. S. A. 1 vol. 12mo, cloth. 
75 cents. 

Manual for Engineer Troops, 

Comprising Drill and Practice for Ponton Bridges, and Pasley's 
Rules for Conducting Operations for a Siege. The Snp, Military 
Mining and Construction of Batteries. By Capt. J. C. Duane, 
TJ. S. Engineers. Plates and woodcuts. 12mo, cloth. Hf. 
mor. $2-00 

New Manual of Sword and Sabre 
Exercife. 

By Captain J. C. Kelton, TJ. S. A. Thirty plates. In Press. 



School of the Guides. 

Designed for the use of the Militia of the United States. Flexible 
cloth. 50 cents. 

"This excellent compilation condenses into a compass of less than sixty 
pages all the instruction necessary for the guides, and the information being 
disconnected with other matters, is more readily referred to and more easily 
acquired." — Louisville Journal. 

" The work is carefully got up, and is illustrated by numerous figures, which 
make the positions of the" guides plain to the commonest understanding. Those 
of our sergeants who wish to l;e ' posted ' in their duties should procure a copy." 
—Sunday Mercury, Philadelphia. 

"It his received high praise, and will prove of great service in perfecting 
the drill of our Militia."— N. American and V. S. Gazette, Phil. 

"This neat hand-book of the elementary movements on which the art of the 
tactician is based, reflects great credit on Col. Le Gal, whose reputation is de- 
servedly high among military men. No soldier should be without the School 
of the Guides."—: New York Daily News. 



Gunnery in 1858 : 

A Treatise on Rifles, Cannon, and Sporting Arms. By TVm. 
Greener, C. E. 1 vol. 8vo, cloth. $3. 

Manual of Heavy Artillery. 

For the Use of Volunteers. 1 vol. 12mo. Red cloth. 75 cents. 

"Should be in the hands of every Artillerist." — N. Y. Illustrated News. 

"This ia a concise and well-prepared Manual, adapted to the wants of Vol- 
unteers. The instruction, which is of an important nature, is presented in a 
simple and clear style, such as will be easily understood. The volume is also 
illustrated with explanatory cuts and drawings. It is a work of practical 
value, and one needed at the present time in the service." — Boston Commercial 
Bulletin. 

" An indispensable Manual for all who wish easily and accurately to learn 
the school of the Artillerist." — N. Y. Commercial Advertiser. 



Auftrian Infantry Tactics. 

Evolutions of the Line as practised by the Austrian Infantry, and 
adopted in 1853. Translated by Capt. C. M. Wilcox, Seventh 
Regiment TJ. S. Infantry. 1 vol. 12mo. Three large plates, 
cloth. $1. 
"The movements of armies engaged in battle have often been compared to 
those of the chess-board, and we cannot doubt that there are certain principles 
of tactics in actual war as in that game, which may determine the result inde- 
pendently, in a great measure, of the personal stn-ngth and courage of the men 
engaged. The difference between these principles as applied in the American 
Army and in the Austrian, is so wide as to have .suggested the translation of 
the work before us, which contains the whole result of the famous Field-Marshal 
Radetzky*s experience for twenty-five years, while ia supreme command in 
Italy."— New York Century. 



J). Van Nostrand^s Publications. 



Hand- Book of Artillery, 

For the Service of the United States Army and Militia. New and 

revised edition. By M;ij. Joseph Egberts, U. S. A. 1 vol. 

ISmo, cloth, New and enlarged edition. $1 00. 

" A complete catechism of gun practice, covering the -whole ground of this 
branch of military science, and adapted to militia and volunteer drill, as veil as 
to the regular army. It has the merit of precise- detail, even to the technical 
names of all parts of a gun, and how the smallest operations connected with its 
use can be best performed. It has evidently been prepared with great care, 
and -with strict scientific accuracy. Ey the recommendation of a committee 
appointed by the commanding officer of the Artillery School at Fort Monroe, 
"Va., it has been substituted for ' Burns' Questions and Answers,' an English 
work which has heretofore been the text-book of instruction in this country." 
— JSew York Century. 



New Infantry Tactics, 

For the Instruction, Exercise, and Manoeuvres of the Soldier, a Com- 
pany, Line of Skirmishers, Battalion, Brigade, or Corps d'Armee. 
By Brig. -Gen. Silas Casey, U. S. A. 3 vols. 24mo. Half roan, 
lithographed plates. $2.50. 
Vol. I. — School of the Soldier ; School of the Company ; In- 

. struction for Skirmishers. 
Vol. II.— School of the Battalion. 

Vol. III. — Evolutions of a Brigade ; Evolutions of a Corps 
d'Armee. 

The manuscript of this new system of Infantry Tactics was carefully ex- 
amined by General MoClet.lan, and met with his unqualified approval, which, 
he has since manifested by authorizing General Casey to adopt it for his entire 
division. The author has retained much that is valuable contained in the sys- 
tems of Scott and Hardee, but has made many important changes and addi- 
tions which experience and the exigencies of the service require. General 
Casey's reputation as an accomplished soldier and skilful tactician is a guar- 
antee that the work he has undertaken has been thoroughly performed. 

"These volumes are based on the French ordonnances of 1831 and 1S45 for 
the manoeuvres of heavy infantry and chasseurs d pied; both of these systems 
have been in use in our service for some years, the former having been trans- 
lated by Gen. Scott, and the latter by Col. Hardee. After the introduction of 
the latter drill in our service, in connection with Gen. Scott's Tactics, there* 
arose the necessity of a uniform system for the manoeuvres of all the infantry 
arm of the service. These volumes are the result of the author's endeavor to 
communicate the instruction, now used and adopted in the army, to achieve 
this result.'' — Boston Journal. 

" Based on the best precedents, adnptcd to the novel requirements of the art 
of war, and very full in its instructions, Casey's Tactics will be received as tho 
most useful and most comprehensive work of its kind in our language. From 
the drill and discipline of the individual soldier, or through all the various 
combinations, to the manoeuvres of a brigade and the evolutions of a Corps 
D'Armee, the student is advanced by a clear method and steady progress. Nu- 
merous cuts, plans, and diagrams illustrate positions and movements, and de- 
monstrate to the eye the exact working out of the individual position, brigading, 
order of battle, &c, &c. The work is a model of publishing success, being in. 
three neat pocket volumes."— flew Yorker. 



D. Van JWbstrand's Publications, 



Scott's Military Dictionary. 

Comprising Technical Definitions; Information on Raising and 
Keeping Troops ; Actual Service, including makeshifts and 
improved materiel, and Law, Government, Regulation, and 
Administration relating to Land Forces. By Colonel H. L. 
Scott, Inspector-General U. S. A. 1 vol., large octavo, fully 
illustrated, half morocco. $5. 

** It is a complete Encyclopaedia of Military Science. 1 '— Philadelphia Even- 
ing Bulletin. 

"We cannot speak too much in legitimate praise of this work." — National 
Intelligencer. 

" It should be made a Text-book for the study of every Volunteer."— Har- 
per's Magazine. 

"We cordially commend it to public favor." — Washington Globe. 

"This comprehensive and skilfully prepared work supplies a want that has 
long been felt, and will be peculiarly valuable at this time as a book of refer- 
ence. 1 '— Boston Commercial Bulletin. 

"The Military Dictionary is splendidly got up in every way, and reflects 
credit on the publisher. The officers of every company in the service should 
possess ft"— N. Y. Tablet. 

"The work is more properly a Military Encyclopaedia, and is profusely illus- 
trated with engravings. It appears to contain every thing that can be wanted 
In the shape of information by officers of ail grades." — Philadelphia North 
American. 

"This book is really an Encyclopaedia, both elementary and technical, and 
as such occupies a gap in military literature which has long been most incon- 
veniently vacant. This book meets a present popular want, and will be secured 
not only by those embarking in the profession but by a great number of civilians, 
who are determined to follow the descriptions and to understand the philoso- 

f)hy of the various movements of the campaign. Indeed, no tolerably good 
ibrary would be complete without the work." — New York Times. 

" The work has evidently been compiled from a careful consultation of the 
best authorities, enriched with the results of the experience and personal 
knowledge of the author." — N. Y Daily Tribune. 

" Works like the present are invaluable. The officers of our Volunteer ser- 
vice would all do well to possess themselves of the volume." — N. Y. Herald. 



New Bayonet Exercise. 

A New Manual of the Bayonet, for the Army and Militia of the United 
States. By Colonel J. C. Keltox, U. S. A. With thirty 
beautifully-engraved plates. Red cloth. $1.75. 

This Manual was prepared for the use of the Corps of Cadets, and has been 
introduced at the Military Academy with satisfactory results. It is simply the 
theory of the attack and defence of the sword applied to the bayonet, on the 
authority of men skilled in the use of arms. 

The Manual contains practical lessons in Fencing, and prescribes the de- 
fence against Cavalry and the manner of conducting a contest with a Swords- 
man. 

"This work merits afavorable reception at the hands of all military men. 
It contains all the instruction necessary to enable an officer to drill his men in 
the use of this weapon. The introduction of the Sabre Bayonet in our Army 
renders e knowledge of tfcti e*er:ise mors imperative."— New York Times. 



D. Van Nostrand's Publication* 



Notes on Sea-Coaft Defence : 

Consisting of Sea-Coast Fortification ; the Fifteen-Inch Gun ; and 
Casemate Embrasures. By Gen. J. G. Barnard, Corps of 
Engineers, U. S. Army. 1 toI. 8vo, cloth, plates. $1 50. 

"This small volume by one of the most accomplished officers In the United 
States service is especially valuable at this time. Concisely and thoroughly 
Major Barnard discusses the subjects included in this volume, and gives infor- 
mation that will be rend with great profit by military men, and by all interested 
in the art of war as a defensive force,"— New York Commercial. 

" It is no light compliment when we say that Major Barnard's book does no 
discredit to the corps to which he belongs. He writes concisely, and with a 
thorough knowledge of his subject." — Russell's Army and Navy Gazette. 



Instructions for Naval Light 
Artillery, 

Afloat and Ashore. By Lieut. S. B. Luce, U. S. N. 1 vol. 8vo, 
with 22 lithographic plates. Cloth. $1.50, 



Steam for the Million. 

A Popular Treatise on Steam and its Application to the Useful 

Arts, especially to Navigation. By J. H. Ward, Commander 

U. S. Navy. New and revised edition. 1 vol. 8vo, cloth. $1. 

"A most excellent work for the young engineer and general reader. Many 
facts relating to the management of the boiler and engine are set forth with a 
simplicity of language, and perfection of detail, that brings the subject home to 
the reader. Mr. Ward is also peculiarly happy in his illustrations."— American 
Engineer. 



Screw Propuliion, 



Notes on Screw Propulsion, its Rise and History. By Capt. W. H. 
Walker, U. S. Navy. 1 vol. 8vo., cloth. 75 cents. 

" Some interesting notes on screw propulsion, its rise and progress, have just 
been issued by Commander W. II. Walker, U. S. N., from which all that is 
likely to be desired on the subject may be readily acquired. * * * * After 
thoroughly demonstrating the efficiency of the screw, Mr. "Walker proceeds to 
point out the various other points to be attended to in order to secure an effi- 
cient man-of-war, and eulogizes throughout the readiness of the British Admi- 
ralty to test every novelty calculated to give satisfactory results. * * * * 
Commander Walker's book contains an immense amount of concise practical 
data, and every item of information recorded fully proves that the various 
points bearing upon it have been well considered previously to expressing an 
opinion." — London Mining Journal. 

" Every engineer should have it in his library." — American Engineer. 



D. Van Nostrand's Publications. 



Sword-Play, 



THE MILITIAMAN'S MANUAL AND SWORD-PLAY WITHOUT 
A MASTER. — Rapier and Broad-Sword Exercises copiously 
Explained and Illustrated; Small- Arm Light Infantry Drill of 
the United States Army ; Infantry Manual of Percussion Mus- 
kets ; Company Drill of the United States Cavalry. By Major 
M. W. Beruiman, engaged for the last thirty years in the prac- 
tical instruction of Military Students. Second edition. 1 vol. 
12mo,, red cloth. $1. 

" Captain Berriman has had thirty years' experience in teaching military 
students, and bis work is written in a simple, clear, and soldierly style. It is 
illustrated with twelve plates, and is one of the cheapest and most complete 
■works of the kind published in this country." —JS J ew York World. 

"This work will be found very valuable to all persons seeking military in- 
struction ; but it recommends itself most especially to officers, and those who 
have to use the sword or sabre. We believe, it is the only work on the use of 
the sword published in this country."— New York Tablet. 

"It is a work of obvious merit and value."— Boston Traveller. 



Military Lav/ and Courts Martial, 

By Capt. S. V. Benet, U. S. Ordnance, Asst. Prof, of Ethics in the 
United States Military Academy. 1 vol. Svo. Law sheep. $3. 



The Artillerift's Manual : 

Compiled from various Sources, and adapted to the Service of the 
United States. Profusely illustrated with woodcuts and engrav- 
ings on stone. Second edition, revised and corrected, with 
valuable additions, in press. By Capt. John Gibbon, U. S. 
Army. 1 vol. Svo, half roan, $5 ; half russia, &6. 

This book is now considered the standard authority for that particular branch 
of the Service in the United States A.rmy. The War Department, at Washing- 
ton, has exhibited its thorough appreciation of the merits of this volume, the 
want of which has been hitherto much felt in the service, by subscribing for TOO 
copies. 

"It is with great pleasure that we welcome the appearance of a new work on 
this subject, entitled 'The Artillerist's Manual, 1 by Capt. John Gibbon, a 
highly scientific and meritorious officer of artillery in our regular service. The 
work, an octavo volume of 500 pages, in larse, clear tvpe, appears to be well 
adapted to supply just what has been heretofore needed to fill the gap between 
the simple Manual and the more abstruse demonstrations of the science of gun- 
nery. The whole work is profusely illustrated with woodcuts and engravings 
on stone, tending to give a more complete and exact idea of the varions'matters 
described in the text. The book may well be considered as a valuable and im- 
portant addition to the military science of the country,"— Jfew York Merald. 



D. Van No strand's Publications. 



Siege of Bomarfund (1854). 

Journals of Operations of the Artillery and Engineers. Published 

by permission of the Minister of War. Illustrated by maps and 

plans. Translated from the French by an Army Officer. 

1 vol. 12mo, cloth. 75 cents. 

"To military men this little volume is of special interest. It contains a 

translation by an officer of the United States Army, of the journal of operations 

by the artillery and engineers at the siege of Bomarsund in 1854, published by 

permission of the French Minister of War in the Journal des Armees speciales 

etdeV Mat Major. The account of the same successful attack, given by Sir 

Howard Douglas in the new edition of his work on Gunnerv. is appended; and 

the narrative is illustrated by elaborate maps and plans."— Ifew York Paper. 



Lefsons and Practical Notes on 
Steam, 

The Steam-Engine, Propellers, &c, &c, for Young Marine Engi- 
neers, Students, and others. By the. late W. R. King, U. S. N. 
Revised by Chief-Engineer J. W. King, IT. S. Navy. Second 
edition, enlarged. 8vo, cloth. $1.50 
"This is the second edition of a valuable work of the late W. E. Kino, 
U. S. N. It contains lessons and practical notes on Steam and the Steam- 
Engine, Propellers, &c. It is calculated to be of great use to young marine en- 
gineers, students, and others. The text is illustrated and explained by numerous 
diagrams and representations of machinery. This new edition has been revised 
ami enlarged by Chief Engineer J. W. King, U. S. N., brother to the deceased 
author of the work."— Boston Daily Advertiser. 

"This is one of the best, because eminently plain and practical, treatises on 
the Steam-Engine ever published." — Philadelphia Press. 

" Its re-publication at this time, when so many young men are entering the 
service as naval engineers, is most opportune. Each of them ought to have a 
copy." — Philadelphia Evening Bulletin. 



Manual of Internal Rules and Reg- 
ulations for Men-of-War. 

By Commodore U. P. Levy, U. S. N., late Flag-officer command- 
ing U. S. Naval Force in the Mediterranean, &c. Flexible 
bine cloth. Second edition, revised and enlarged. 50 cents. 

"Among the professional publications for wh'ch we are indebted to the war, 
we willingly give a prominent place to this useful little Manual of Pailes and 
Regulations to be observed on board of ships of war. Its authorship is a sum- 
dent guarantee for its accuracy and practical value ; and as a gn:de to young 
officers in providing for the discipline, police, and sanitary government of the 
vessels under their command, we know of nothing superior."— iv. Y. Herald. 

"Should be in the hands of every Naval officer, of whatever grade, and will 
not come amiss to any intelligent mariner."— Boston Traveller. 

" A work which will prove of (treat utilitv, in both the Naval service and 
the mercantile marine." — Baltimore American. 



~M 



D. Van Kostrand' } s Publications. 

Gunnery Instructions. 

Simplified for the "Volunteer Officers of the U. S. Navy, with hints to 
Executive and other Officers. By Lieut.-Commander Edward 
Barrett, U. S. N., Instructor in Gunnery, Navy Yard, Brook- 
lyn. Third edition, revised and enlarged. 1 vol. 12mo, cloth. 
$1 25. 

"It is a thorough work, treating plainly on its subject, and contains also some 
valuable hints to executive officers. No officer in the volunteer navy should be 
•without a copy." — Boston Evening Traveller. 

"This work contains detailed and specific instructions on all points connected 
with the use and management of guns of every kind in the naval service. It has 
full illustrations, and many of these of the most elementary character, especially 
designed for the use of volunteers in the navy. The duties of executive officers 
and of the division officers are so clearly set forth, that ' he who runs may read' 
and understand. The manual exercise is explicit, and rendered simple by dia- 
grams. Forms of watch and quarter bills are given; and at the close there is a 
table of ranges according to the kind and calibre of gun, the weight of the ball, 
and the charge of powder. A valuable little hand-book."— Philadelphia In- 
quirer. 

" I have looked through Lieut. Barrett's book, and think it will be very valu- 
able to the volunteer officers who are now in the naval service. 

"C. E. P. EODGEBS, 
Commanding U. S. Steam Frigate Wabash." 



The " C. S. A." and the Battle of 
Bull Run. 

(A Letter to an English Friend.) By J. G. Barxard, Major of Engi- 
neers, U. S. A., Brigadier-General, and Chief Engineer, Army of 
the Potomac. With five maps. 1 vol. 8vo, cloth. %1 50. 

" This book was begun by the author as a letter to a friend in England, but as 
he proceeded and his MSS. increased in magnitude, he changed his original plan, 
and the book is the result General Barnard gives by far the best, most compre- 
hensible and complete account of the Battle of Bull Eun we have seen. It is il- 
lustrated by some beautifully drawn maps, prepared for the War Department by 
the topographical engineers. He demonstrates to a certainty that but for the 
causeless panic the day might not have been lost. The author writes with vigor 
and earnestness, and has contributed one of the most valuable records yet pub- 
lished of the history of the war. ,, — Boston Commercial Bulletin. 



Models of Fortifications. 

Vauban's First System — One Front and two Bastions ; Scale, 20 yards 
to an inch. The Modern System — One Front; Scale 20 yards 
to an inch. Field- Works — The Square Redoubt ; Scale, 5 yards 
to an inch. Mr. Kimber's three volumes, viz. : Vauban's First 
System, The Modern System, and Field- Works, will accompany 
the Models. Price for the Set of Three, with books, $60. 



.-J 



